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  <p>
    
      <a href="http://www.w3.org/"><img width="72" height="48" src="http://www.w3.org/Icons/w3c_home" alt="W3C" /></a>
    
  </p>
  <h1 class="title" id="title">JSON-LD Syntax 1.0</h1>
  
    <h2 id="subtitle">A JSON Serialization for Linking Data</h2>
  
  <h2 id="w3c-editor-s-draft-25-december-2012"><abbr title="World Wide Web Consortium">W3C</abbr> Editor's Draft 25 December 2012</h2>
  <dl>
    
      <dt>This version:</dt>
      <dd><a href="http://dvcs.w3.org/hg/json-ld/raw-file/default/spec/ED/json-ld-syntax/20121225/index.html">http://dvcs.w3.org/hg/json-ld/raw-file/default/spec/ED/json-ld-syntax/20121225/index.html</a></dd>
      <dt>Latest published version:</dt>
      <dd><a href="http://www.w3.org/TR/json-ld-syntax/">http://www.w3.org/TR/json-ld-syntax/</a></dd>
    
    
      <dt>Latest editor's draft:</dt>
      <dd><a href="http://dvcs.w3.org/hg/json-ld/raw-file/default/spec/latest/json-ld-syntax/index.html">http://dvcs.w3.org/hg/json-ld/raw-file/default/spec/latest/json-ld-syntax/index.html</a></dd>
    
    
    
    
      
    
    
    
    <dt>Editors:</dt>
    <dd rel="bibo:editor" inlist=""><span typeof="foaf:Person"><a rel="foaf:homepage" property="foaf:name" content="Manu Sporny" href="http://manu.sporny.org/">Manu Sporny</a>, <a rel="foaf:workplaceHomepage" href="http://digitalbazaar.com/">Digital Bazaar</a></span>
</dd>
<dd rel="bibo:editor" inlist=""><span typeof="foaf:Person"><a rel="foaf:homepage" property="foaf:name" content="Gregg Kellogg" href="http://greggkellogg.net/">Gregg Kellogg</a>, <a rel="foaf:workplaceHomepage" href="http://kellogg-assoc.com/">Kellogg Associates</a></span>
</dd>
<dd rel="bibo:editor" inlist=""><span typeof="foaf:Person"><a rel="foaf:homepage" property="foaf:name" content="Markus Lanthaler" href="http://www.markus-lanthaler.com/">Markus Lanthaler</a>, <a rel="foaf:workplaceHomepage" href="http://www.tugraz.at/">Graz University of Technology</a></span>
</dd>

    
      <dt>Authors:</dt>
      <dd rel="dcterms:contributor"><span typeof="foaf:Person"><a rel="foaf:homepage" property="foaf:name" content="Manu Sporny" href="http://digitalbazaar.com/">Manu Sporny</a>, <a rel="foaf:workplaceHomepage" href="http://digitalbazaar.com/">Digital Bazaar</a></span>
</dd>
<dd rel="dcterms:contributor"><span typeof="foaf:Person"><a rel="foaf:homepage" property="foaf:name" content="Dave Longley" href="http://digitalbazaar.com/">Dave Longley</a>, <a rel="foaf:workplaceHomepage" href="http://digitalbazaar.com/">Digital Bazaar</a></span>
</dd>
<dd rel="dcterms:contributor"><span typeof="foaf:Person"><a rel="foaf:homepage" property="foaf:name" content="Gregg Kellogg" href="http://greggkellogg.net/">Gregg Kellogg</a>, <a rel="foaf:workplaceHomepage" href="http://kellogg-assoc.com/">Kellogg Associates</a></span>
</dd>
<dd rel="dcterms:contributor"><span typeof="foaf:Person"><a rel="foaf:homepage" property="foaf:name" content="Markus Lanthaler" href="http://www.markus-lanthaler.com/">Markus Lanthaler</a>, <a rel="foaf:workplaceHomepage" href="http://www.tugraz.at/">Graz University of Technology</a></span>
</dd>
<dd rel="dcterms:contributor"><span typeof="foaf:Person"><a rel="foaf:homepage" property="foaf:name" content="Mark Birbeck" href="http://webbackplane.com/">Mark Birbeck</a>, <a rel="foaf:workplaceHomepage" href="http://webbackplane.com/">Backplane Ltd.</a></span>
</dd>

    
  </dl>
  
  
    <p>
      
        This document is also available in this non-normative format: 
      
      <a href="diff-20120930.html">diff to previous version</a>
    </p>
  
  
  
    
      <p class="copyright">
        <a href="http://www.w3.org/Consortium/Legal/ipr-notice#Copyright">Copyright</a> © 
        2010-2012
        
        <a href="http://www.w3.org/"><abbr title="World Wide Web Consortium">W3C</abbr></a><sup>®</sup> 
        (<a href="http://www.csail.mit.edu/"><abbr title="Massachusetts Institute of Technology">MIT</abbr></a>,
        <a href="http://www.ercim.eu/"><abbr title="European Research Consortium for Informatics and Mathematics">ERCIM</abbr></a>,
        <a href="http://www.keio.ac.jp/">Keio</a>), All Rights Reserved.
        <abbr title="World Wide Web Consortium">W3C</abbr> <a href="http://www.w3.org/Consortium/Legal/ipr-notice#Legal_Disclaimer">liability</a>,
        <a href="http://www.w3.org/Consortium/Legal/ipr-notice#W3C_Trademarks">trademark</a> and
        <a href="http://www.w3.org/Consortium/Legal/copyright-documents">document use</a> rules apply.
      </p>
    
  
  <hr />
</div>
<section id="abstract" class="introductory" property="dcterms:abstract" datatype="" typeof="bibo:Chapter" resource="#abstract" rel="bibo:chapter"><h2>Abstract</h2>
<p>
JSON has proven to be a highly useful object serialization and messaging format.
In an attempt to harmonize the representation of <a class="tref internalDFN" title="linked_data" href="#dfn-linked_data">Linked Data</a>
in JSON, this specification outlines a common JSON representation format for
expressing directed graphs; mixing both Linked Data and non-Linked Data in
a single document.
</p>
</section><section id="sotd" class="introductory" typeof="bibo:Chapter" resource="#sotd" rel="bibo:chapter"><h2>Status of This Document</h2>
  
    
      
        <p>
          <em>This section describes the status of this document at the time of its publication. Other
          documents may supersede this document. A list of current <abbr title="World Wide Web Consortium">W3C</abbr> publications and the latest revision
          of this technical report can be found in the <a href="http://www.w3.org/TR/"><abbr title="World Wide Web Consortium">W3C</abbr> technical reports
          index</a> at http://www.w3.org/TR/.</em>
        </p>
        
<p>This document has been under development for over 20 months in the
JSON for Linking Data Community Group. The document has recently been
transferred to the RDF Working Group for review, improvement, and publication
along the Recommendation track. The specification has undergone significant
development, review, and changes during the course of the last 20 months.
</p>
<p>There are several independent
<a href="http://json-ld.org/#impl">interoperable implementations</a> of
this specification. There is
a <a href="https://github.com/json-ld/json-ld.org/tree/main/test-suite">fairly complete test suite</a>
and a <a href="http://json-ld.org/playground/">live JSON-LD editor</a>
that is capable of demonstrating the features described in
this document. While development on implementations, the test suite
and the live editor will continue, they are believed to be mature enough
to be integrated into a non-production system at this point in time with
the expectation that they could be used in a production system within the
next year.
</p>

<p>There are a number of ways that one may participate in the development of
this specification:</p>

<ul>
  <li>If you want to make sure that your feedback is formally addressed by
    the RDF Working Group, you should send it to public-rdf-comments:
    <a href="http://lists.w3.org/Archives/Public/public-rdf-comments/">public-rdf-comments@w3.org</a></li>

  <li>Ad-hoc technical discussion primarily occurs on the public community mailing list:
    <a href="http://lists.w3.org/Archives/Public/public-linked-json/">public-linked-json@w3.org</a></li>

  <li><a href="http://json-ld.org/minutes/">Public JSON-LD Community Group teleconferences</a>
  are held on Tuesdays at 1500UTC every week.</li>

  <li>RDF Working Group teleconferences are held on Wednesdays at 1500UTC
  every week. Participation is limited to RDF Working Group members.</li>

  <li>Specification bugs and issues should be reported in the
    <a href="https://github.com/json-ld/json-ld.org/issues">issue tracker</a>
    if you do not want to send an e-mail to the public-rdf-comments mailing
    list.</li>

  <li><a href="https://github.com/json-ld/json-ld.org/tree/main/spec">Source code</a>
    for the specification can be found on Github.</li>

  <li>The <a href="http://webchat.freenode.net/?channels=json-ld">#json-ld</a>
    IRC channel is available for real-time discussion on irc.freenode.net.</li>
</ul>


        <p>
          This document was published by the <a href="http://www.w3.org/2011/rdf-wg/">RDF Working Group</a> as an Editor's Draft.
          
          If you wish to make comments regarding this document, please send them to 
          <a href="mailto:public-rdf-comments@w3.org">public-rdf-comments@w3.org</a> 
          (<a href="mailto:public-rdf-comments-request@w3.org?subject=subscribe">subscribe</a>,
          <a href="http://lists.w3.org/Archives/Public/public-rdf-comments/">archives</a>).
          
          
          All feedback is welcome.
        </p>
        
          <p>
            Publication as an Editor's Draft does not imply endorsement by the <abbr title="World Wide Web Consortium">W3C</abbr> Membership.
            This is a draft document and may be updated, replaced or obsoleted by other documents at 
            any time. It is inappropriate to cite this document as other than work in progress.
          </p>
        
        
        <p>
          
            This document was produced by a group operating under the 
            <a href="http://www.w3.org/Consortium/Patent-Policy-20040205/">5 February 2004 <abbr title="World Wide Web Consortium">W3C</abbr> Patent Policy</a>.
          
          
          
            
              <abbr title="World Wide Web Consortium">W3C</abbr> maintains a <a href="http://www.w3.org/2004/01/pp-impl/46168/status" rel="disclosure">public list of any patent disclosures</a> 
            
            made in connection with the deliverables of the group; that page also includes instructions for 
            disclosing a patent. An individual who has actual knowledge of a patent which the individual believes contains
            <a href="http://www.w3.org/Consortium/Patent-Policy-20040205/#def-essential">Essential Claim(s)</a> must disclose the
            information in accordance with <a href="http://www.w3.org/Consortium/Patent-Policy-20040205/#sec-Disclosure">section
            6 of the <abbr title="World Wide Web Consortium">W3C</abbr> Patent Policy</a>.
          
          
        </p>
        
      
    
  
</section><section id="toc"><h2 class="introductory">Table of Contents</h2><ul class="toc"><li class="tocline"><a href="#introduction" class="tocxref"><span class="secno">1. </span>Introduction</a><ul class="toc"><li class="tocline"><a href="#how-to-read-this-document" class="tocxref"><span class="secno">1.1 </span>How to Read this Document</a></li></ul></li><li class="tocline"><a href="#design-goals-and-rationale" class="tocxref"><span class="secno">2. </span>Design Goals and Rationale</a></li><li class="tocline"><a href="#terminology" class="tocxref"><span class="secno">3. </span>Terminology</a><ul class="toc"><li class="tocline"><a href="#general-terminology" class="tocxref"><span class="secno">3.1 </span>General Terminology</a></li><li class="tocline"><a href="#syntax-tokens-and-keywords" class="tocxref"><span class="secno">3.2 </span>Syntax Tokens and Keywords</a></li></ul></li><li class="tocline"><a href="#conformance" class="tocxref"><span class="secno">4. </span>Conformance</a></li><li class="tocline"><a href="#basic-concepts" class="tocxref"><span class="secno">5. </span>Basic Concepts</a><ul class="toc"><li class="tocline"><a href="#the-context" class="tocxref"><span class="secno">5.1 </span>The Context</a></li><li class="tocline"><a href="#from-json-to-json-ld" class="tocxref"><span class="secno">5.2 </span>From JSON to JSON-LD</a></li><li class="tocline"><a href="#iris" class="tocxref"><span class="secno">5.3 </span>IRIs</a></li><li class="tocline"><a href="#node-identifiers" class="tocxref"><span class="secno">5.4 </span>Node Identifiers</a></li><li class="tocline"><a href="#specifying-the-type" class="tocxref"><span class="secno">5.5 </span>Specifying the Type</a></li><li class="tocline"><a href="#string-internationalization" class="tocxref"><span class="secno">5.6 </span>String Internationalization</a></li><li class="tocline"><a href="#json-ld-syntax" class="tocxref"><span class="secno">5.7 </span>JSON-LD Syntax</a></li></ul></li><li class="tocline"><a href="#advanced-concepts" class="tocxref"><span class="secno">6. </span>Advanced Concepts</a><ul class="toc"><li class="tocline"><a href="#compact-iris" class="tocxref"><span class="secno">6.1 </span>Compact IRIs</a></li><li class="tocline"><a href="#typed-values" class="tocxref"><span class="secno">6.2 </span>Typed Values</a></li><li class="tocline"><a href="#language-tagged-strings" class="tocxref"><span class="secno">6.3 </span>Language-tagged Strings</a></li><li class="tocline"><a href="#referencing-contexts-from-json-documents" class="tocxref"><span class="secno">6.4 </span>Referencing Contexts from JSON Documents</a></li><li class="tocline"><a href="#expanded-term-definition" class="tocxref"><span class="secno">6.5 </span>Expanded Term Definition</a></li><li class="tocline"><a href="#type-coercion" class="tocxref"><span class="secno">6.6 </span>Type Coercion</a></li><li class="tocline"><a href="#property-generators" class="tocxref"><span class="secno">6.7 </span>Property Generators</a></li><li class="tocline"><a href="#iri-expansion-within-a-context" class="tocxref"><span class="secno">6.8 </span><abbr title="Internationalized Resource Identifier">IRI</abbr> Expansion Within a Context</a></li><li class="tocline"><a href="#sets-and-lists" class="tocxref"><span class="secno">6.9 </span>Sets and Lists</a></li><li class="tocline"><a href="#embedding" class="tocxref"><span class="secno">6.10 </span>Embedding</a></li><li class="tocline"><a href="#named-graphs" class="tocxref"><span class="secno">6.11 </span>Named Graphs</a></li><li class="tocline"><a href="#identifying-blank-nodes" class="tocxref"><span class="secno">6.12 </span>Identifying Blank Nodes</a></li><li class="tocline"><a href="#aliasing-keywords" class="tocxref"><span class="secno">6.13 </span>Aliasing Keywords</a></li><li class="tocline"><a href="#data-annotations" class="tocxref"><span class="secno">6.14 </span>Data Annotations</a></li><li class="tocline"><a href="#explicitly-ignoring-data" class="tocxref"><span class="secno">6.15 </span>Explicitly Ignoring Data</a></li><li class="tocline"><a href="#expanded-document-form" class="tocxref"><span class="secno">6.16 </span>Expanded Document Form</a></li><li class="tocline"><a href="#compact-document-form" class="tocxref"><span class="secno">6.17 </span>Compact Document Form</a></li></ul></li><li class="tocline"><a href="#data-model" class="tocxref"><span class="secno">A. </span>Data Model</a></li><li class="tocline"><a href="#json-ld-grammar" class="tocxref"><span class="secno">B. </span>JSON-LD Grammar</a><ul class="toc"><li class="tocline"><a href="#grammar-node-object" class="tocxref"><span class="secno">B.1 </span>Node Object</a></li><li class="tocline"><a href="#grammar-term-reference" class="tocxref"><span class="secno">B.2 </span>Term</a></li><li class="tocline"><a href="#grammar-language-map" class="tocxref"><span class="secno">B.3 </span>Language Map</a></li><li class="tocline"><a href="#grammar-annotation-map" class="tocxref"><span class="secno">B.4 </span>Annotation Map</a></li><li class="tocline"><a href="#grammar-expanded-values" class="tocxref"><span class="secno">B.5 </span>Expanded Values</a></li><li class="tocline"><a href="#grammar-set-list" class="tocxref"><span class="secno">B.6 </span>List and Set Values</a></li><li class="tocline"><a href="#grammar-context" class="tocxref"><span class="secno">B.7 </span>Context Definition</a></li></ul></li><li class="tocline"><a href="#relationship-to-rdf" class="tocxref"><span class="secno">C. </span>Relationship to RDF</a></li><li class="tocline"><a href="#relationship-to-other-linked-data-formats" class="tocxref"><span class="secno">D. </span>Relationship to Other Linked Data Formats</a><ul class="toc"><li class="tocline"><a href="#turtle" class="tocxref"><span class="secno">D.1 </span>Turtle</a><ul class="toc"><li class="tocline"><a href="#prefix-definitions" class="tocxref"><span class="secno">D.1.1 </span>Prefix definitions</a></li><li class="tocline"><a href="#embedding-1" class="tocxref"><span class="secno">D.1.2 </span>Embedding</a></li><li class="tocline"><a href="#lists" class="tocxref"><span class="secno">D.1.3 </span>Lists</a></li></ul></li><li class="tocline"><a href="#rdfa" class="tocxref"><span class="secno">D.2 </span>RDFa</a></li><li class="tocline"><a href="#microformats" class="tocxref"><span class="secno">D.3 </span>Microformats</a></li><li class="tocline"><a href="#microdata" class="tocxref"><span class="secno">D.4 </span>Microdata</a></li></ul></li><li class="tocline"><a href="#iana-considerations" class="tocxref"><span class="secno">E. </span>IANA Considerations</a></li><li class="tocline"><a href="#acknowledgements" class="tocxref"><span class="secno">F. </span>Acknowledgements</a></li><li class="tocline"><a href="#references" class="tocxref"><span class="secno">G. </span>References</a><ul class="toc"><li class="tocline"><a href="#normative-references" class="tocxref"><span class="secno">G.1 </span>Normative references</a></li><li class="tocline"><a href="#informative-references" class="tocxref"><span class="secno">G.2 </span>Informative references</a></li></ul></li></ul></section>



<section class="informative" id="introduction">
  
<!--OddPage-->
<h2><span class="secno">1. </span>Introduction</h2><p><em>This section is non-normative.</em></p>

  <p><dfn title="linked_data" id="dfn-linked_data">Linked Data</dfn> is a technique for creating a network
    of inter-connected data across different documents and Web sites. In general,
    Linked Data has four properties: 1) it uses <a class="tref internalDFN" title="iri" href="#dfn-iri">IRIs</a>
    to name things; 2) it uses HTTP <a class="tref internalDFN" title="iri" href="#dfn-iri">IRIs</a>
    for those names; 3) the name <a class="tref internalDFN" title="iri" href="#dfn-iri">IRIs</a>, when dereferenced,
    provide more information about the name; and 4) the data expresses links
    to data on other Web sites. These properties allow data published on the Web
    to work much like Web pages do today. One can start at one piece of Linked Data,
    and follow the links to other pieces of data that are hosted on different
    sites across the Web.</p>

  <p>JSON-LD is designed as a lightweight syntax to express <a class="tref internalDFN" title="linked_data" href="#dfn-linked_data">Linked Data</a> in
    JSON [<cite><a class="bibref" href="#bib-RFC4627">RFC4627</a></cite>]. It is primarily intended to be a way to use Linked Data in
    Web-based programming environments. It is also useful when building interoperable
    Web services and when storing Linked Data in JSON-based storage engines. Since
    JSON-LD is 100% compatible with JSON the large number of JSON parsers and libraries
    available today can be reused. Additionally to all the features JSON provides,
    JSON-LD introduces:</p>

  <ul>
    <li>a universal identifier mechanism for <a class="tref internalDFN" title="json_object" href="#dfn-json_object">JSON objects</a> via the
      use of <a class="tref internalDFN" title="iri" href="#dfn-iri">IRIs</a>,</li>
    <li>a way to disambiguate the keys used between multiple JSON documents
      by mapping them to <a class="tref internalDFN" title="iri" href="#dfn-iri">IRIs</a> via a <a class="tref internalDFN" title="context" href="#dfn-context">context</a>,</li>
    <li>a mechanism in which a value in a <a class="tref internalDFN" title="json_object" href="#dfn-json_object">JSON object</a> may refer
      to a <a class="tref internalDFN" title="json_object" href="#dfn-json_object">JSON object</a> on a different site on the Web,</li>
    <li>the ability to express the language associated with a <a class="tref internalDFN" title="string" href="#dfn-string">string</a></li>
    <li>a way to associate datatypes with values such as dates, times, weights,
      and distances,</li>
    <li>and a facility to express one or more directed graphs, such as a social
      network, in a single document.</li>
  </ul>

  <p>Developers that require any of the facilities listed above or need to serialize
    an RDF graph or dataset [<cite><a class="bibref" href="#bib-RDF-CONCEPTS">RDF-CONCEPTS</a></cite>] in a JSON-based syntax will find
    JSON-LD of interest. The syntax is designed to not disturb already deployed
    systems running on JSON, but provide a smooth upgrade path from JSON to
    JSON-LD.</p>

  <section id="how-to-read-this-document">
    <h3><span class="secno">1.1 </span>How to Read this Document</h3><p><em>This section is non-normative.</em></p>

    <p>This document is a detailed specification for a serialization of Linked
      Data in JSON. The document is primarily intended for the following audiences:</p>

    <ul>
      <li>Software developers that want to encode Linked Data in a variety of
      programing languages that can use JSON.</li>
      <li>Software developers that want to understand the design decisions and
      language syntax for JSON-LD.</li>
      <li>Software developers that want to implement processors and APIs for
      JSON-LD.</li>
    </ul>

    <p>This specification does not describe the programming interfaces for the
      JSON-LD Syntax. The specification that describes the programming interfaces
      for JSON-LD documents is the JSON-LD Application Programming Interface
      [<cite><a class="bibref" href="#bib-JSON-LD-API">JSON-LD-API</a></cite>].</p>

    <p>To understand the basics in this specification you must first be familiar with
      JSON, which is detailed in [<cite><a class="bibref" href="#bib-RFC4627">RFC4627</a></cite>].</p>
  </section>
</section>

<section class="informative" id="design-goals-and-rationale">

<!--OddPage-->
<h2><span class="secno">2. </span>Design Goals and Rationale</h2><p><em>This section is non-normative.</em></p>

<p>A number of design goals were established before the creation of this
  markup language:</p>

<dl>
 <dt>Simplicity</dt>
 <dd>No extra
 processors or software libraries should be necessary to use JSON-LD in its most
 basic form. The language will provide developers with a very easy
 learning curve. Developers only need to know JSON and two
 <a class="tref internalDFN" title="keyword" href="#dfn-keyword">keywords</a> (<code>@context</code>
 and <code>@id</code>) to use the basic functionality in JSON-LD.</dd>
 <dt>Compatibility</dt>
 <dd>The JSON-LD markup must be 100% compatible with JSON. This ensures that
 all of the standard JSON libraries work seamlessly with JSON-LD documents.</dd>
 <dt>Expressiveness</dt>
 <dd>The syntax must be able to express directed graphs, which have been proven
 to be able to express almost every real world data model.</dd>
 <dt>Terseness</dt>
 <dd>The JSON-LD syntax must be very terse and human readable, requiring as
 little effort as possible from the developer.</dd>
 
<!--<dt>Pragmatism</dt>
 <dd>Mixing the expression of pure Linked Data with data that is not
 linked was an approach that was driven by pragmatism. JSON-LD attempts to be
 more practical than theoretical in its approach to Linked Data.</dd>-->

 <dt>Zero Edits, most of the time</dt>
 <dd>JSON-LD must provide a
 <a href="#referencing-contexts-from-json-documents">mechanism</a>
 that allows developers to reference <a class="tref internalDFN" title="context" href="#dfn-context">contexts</a> in
 responses using plain old JSON. This allows organizations that have
 already deployed large JSON-based infrastructure to use JSON-LD's features
 in a way that is not disruptive to their day-to-day operations and is
 transparent to their current customers. At times, mapping JSON to
 a graph representation can become difficult. In these instances, rather than
 having JSON-LD support an esoteric use case, we chose not to support the
 use case and support a simplified syntax instead. So, while Zero Edits is
 a design goal, it is not always possible without adding great complexity to
 the language.
 </dd>
 <dt>One-pass Processing</dt>
 <dd>JSON-LD supports one-pass processing, which results in a very small memory
 footprint when processing documents. For example, to expand a JSON-LD document
 from a compacted form, only one pass is required over the data.</dd>
 
<!--<dt>Linked Data-centric</dt>
 <dd>The focus on Linked Data is placed at a much higher priority than the
 focus on the Semantic Web. One outcome of this ordering of
 priorities is an aggressively reduced focus on the Semantic Web stack.
 While this may be off-putting to proponents of the Semantic Web, the audience
 for this specification are Web developers that want a gentler introduction
 and a simpler technology stack for using Linked Data in their Web applications.
 Semantic Web concepts, such as conversion to and from RDF, are fully supported
 by JSON-LD, but the implementation of these features are not elaborated upon
 in this specification. See <a href="#relationship-to-other-linked-data-formats"></a>
 for more information about how JSON-LD integrates into the more traditional
 Semantic Web stack.
 </dd>-->

</dl>
</section>

<section class="normative" id="terminology">

<!--OddPage-->
<h2><span class="secno">3. </span>Terminology</h2>

<section id="general-terminology">
  <h3><span class="secno">3.1 </span>General Terminology</h3>

  <p>This document uses the following terms as defined in JSON [<cite><a class="bibref" href="#bib-RFC4627">RFC4627</a></cite>]. Refer
    to the <em>JSON Grammar</em> section in [<cite><a class="bibref" href="#bib-RFC4627">RFC4627</a></cite>] for formal definitions.</p>

  <dl>
    <dt><dfn title="json_object" id="dfn-json_object">JSON object</dfn></dt><dd>
      An object structure is represented as a pair of curly brackets
      surrounding zero or more key-value pairs. A key is a
      <a class="tref internalDFN" title="string" href="#dfn-string">string</a>. A single colon comes after each key, separating the
      key from the value. A single comma separates a value from a following
      key.
    </dd>
    <dt><dfn title="array" id="dfn-array">array</dfn></dt>
    <dd>
      An array structure is represented as square brackets surrounding zero
      or more values (or elements). Elements are separated by commas.
      In JSON, an array is an <em>ordered</em> sequence of zero or more values.
      While JSON-LD uses the same array representation as JSON,
      the collection is <em>unordered</em> by default. While order is
      preserved in regular JSON arrays, it is not in regular JSON-LD arrays
      unless specific markup is provided (see <a href="#sets-and-lists" class="sec-ref"><span class="secno">6.9</span> <span class="sec-title">Sets and Lists</span></a>).</dd>
    <dt><dfn title="string" id="dfn-string">string</dfn></dt><dd>
      A string is a sequence of zero or more Unicode characters,
      wrapped in double quotes, using backslash escapes (if necessary). A
      character is represented as a single character string.</dd>
    <dt><dfn title="number" id="dfn-number">number</dfn></dt>
    <dd>
      A number is similar to that used in most programming languages, except
      that the octal and hexadecimal formats are not used and that leading
      zeros are not allowed.</dd>
    <dt><dfn title="true" id="dfn-true">true</dfn> and <dfn title="false" id="dfn-false">false</dfn></dt><dd>
      Values that are used to express one of two possible boolean states.</dd>
    <dt><dfn title="null" id="dfn-null">null</dfn></dt>
    <dd>The <a class="tref internalDFN" title="null" href="#dfn-null">null</a> value. A key-value pair in the
      <code>@context</code> where the value, or the <code>@id</code> of the
      value, is <a class="tref internalDFN" title="null" href="#dfn-null">null</a> explicitly decouples a term's association
      with an <abbr title="Internationalized Resource Identifier">IRI</abbr>. A key-value pair in the body of a JSON-LD document whose
      value is <a class="tref internalDFN" title="null" href="#dfn-null">null</a> has the same meaning as if the key-value pair
      was not defined. If <code>@value</code>, <code>@list</code>, or
      <code>@set</code> is set to <a class="tref internalDFN" title="null" href="#dfn-null">null</a> in expanded form, then
      the entire <a class="tref internalDFN" title="json_object" href="#dfn-json_object">JSON object</a> is ignored.</dd>
  </dl>
</section>

<section id="syntax-tokens-and-keywords">
<h3><span class="secno">3.2 </span>Syntax Tokens and Keywords</h3>

<p>JSON-LD specifies a number of syntax tokens and <dfn title="keyword" id="dfn-keyword">keywords</dfn>
that are a core part of the language:</p>

<dl>
<dt><code>@context</code></dt>
<dd>Used to define the short-hand names that are used throughout a JSON-LD
  document. These short-hand names are called <a class="tref internalDFN" title="term" href="#dfn-term">terms</a> and help
  developers to express specific identifiers in a compact manner. The
  <code>@context</code> keyword is described in detail in the section titled
  <a href="#the-context" class="sec-ref"><span class="secno">5.1</span> <span class="sec-title">The Context</span></a>.</dd>
<dt><code>@id</code></dt>
<dd>Used to uniquely identify <em>things</em> that are being described in the document.
  This keyword is described in <a href="#node-identifiers" class="sec-ref"><span class="secno">5.4</span> <span class="sec-title">Node Identifiers</span></a>.</dd>
<dt><code>@value</code></dt>
<dd>Used to specify the data that is associated with a particular
  <a class="tref internalDFN" title="property" href="#dfn-property">property</a> in the graph. This keyword is described in
  <a href="#string-internationalization" class="sec-ref"><span class="secno">5.6</span> <span class="sec-title">String Internationalization</span></a> and
  <a href="#typed-values" class="sec-ref"><span class="secno">6.2</span> <span class="sec-title">Typed Values</span></a>.</dd>
<dt><code>@language</code></dt>
<dd>Used to specify the native language for a particular value or the default
  language of a JSON-LD document. This keyword is described in the section titled
  <a href="#string-internationalization" class="sec-ref"><span class="secno">5.6</span> <span class="sec-title">String Internationalization</span></a>.</dd>
<dt><code>@type</code></dt>
<dd>Used to set the data type of a <a class="tref internalDFN" title="node" href="#dfn-node">node</a> or
  <a class="tref internalDFN" title="typed_value" href="#dfn-typed_value">typed value</a>. This keyword is described in the section titled
  <a href="#typed-values" class="sec-ref"><span class="secno">6.2</span> <span class="sec-title">Typed Values</span></a>.</dd>
<dt><code>@container</code></dt>
<dd>Used to set the container of a particular value.
  This keyword is described in the section titled <a href="#sets-and-lists" class="sec-ref"><span class="secno">6.9</span> <span class="sec-title">Sets and Lists</span></a>.</dd>
<dt><code>@list</code></dt>
<dd>Used to express an ordered set of data.
  This keyword is described in the section titled <a href="#sets-and-lists" class="sec-ref"><span class="secno">6.9</span> <span class="sec-title">Sets and Lists</span></a>.</dd>
<dt><code>@set</code></dt>
<dd>Used to express an unordered set of data and to ensure that values are always
  represented as arrays. This keyword is described in the section titled
  <a href="#sets-and-lists" class="sec-ref"><span class="secno">6.9</span> <span class="sec-title">Sets and Lists</span></a>.</dd>
<dt><code>@annotation</code></dt>
<dd>Used to specify that a container is used to index information and
  that processing should continue deeper into a JSON data structure.
  This keyword is described in the section titled
  <a href="#data-annotations" class="sec-ref"><span class="secno">6.14</span> <span class="sec-title">Data Annotations</span></a>.</dd>
<dt><code>@vocab</code></dt>
<dd>Used to expand properties and values in <code>@type</code> with a common prefix
  <a class="tref internalDFN" title="iri" href="#dfn-iri"><abbr title="Internationalized Resource Identifier">IRI</abbr></a>. This keyword is described in section <a href="#iris" class="sec-ref"><span class="secno">5.3</span> <span class="sec-title">IRIs</span></a>.</dd>
<dt><code>@graph</code></dt><dd>Used to explicitly label a <a class="tref internalDFN" title="json-ld_graph" href="#dfn-json-ld_graph">JSON-LD graph</a>.
  This keyword is described in <a href="#named-graphs" class="sec-ref"><span class="secno">6.11</span> <span class="sec-title">Named Graphs</span></a>.</dd>
<dt><code>:</code></dt>
<dd>The separator for JSON keys and values that use
  <a class="tref internalDFN" title="compact_iri" href="#dfn-compact_iri">compact IRIs</a>.</dd>
</dl>

<p>For the avoidance of doubt, all keys, <a class="tref internalDFN" title="keyword" href="#dfn-keyword">keywords</a>, and values in JSON-LD are
case-sensitive.</p>
</section>

</section>

<section class="normative" id="conformance">

<!--OddPage-->
<h2><span class="secno">4. </span>Conformance</h2>

<p>The JSON-LD Syntax specification describes the conformance criteria for JSON-LD documents (relevant to authors and authoring tool implementors).</p>

<p>A <a class="tref internalDFN" title="json-ld_document" href="#dfn-json-ld_document">JSON-LD document</a> complies with this specification if it follows the normative statements for documents defined in sections <a href="#referencing-contexts-from-json-documents" class="sec-ref"><span class="secno">6.4</span> <span class="sec-title">Referencing Contexts from JSON Documents</span></a> and <a href="#json-ld-grammar" class="sec-ref"><span class="secno">B.</span> <span class="sec-title">JSON-LD Grammar</span></a>. For convenience, normative statements for documents are often phrased as statements on the properties of the document.</p>

<p>The key words <em class="rfc2119" title="must">must</em>, <em class="rfc2119" title="must not">must not</em>, <em class="rfc2119" title="required">required</em>, <em class="rfc2119" title="shall">shall</em>, <em class="rfc2119" title="shall not">shall not</em>, <em class="rfc2119" title="should">should</em>, <em class="rfc2119" title="should not">should not</em>, <em class="rfc2119" title="recommended">recommended</em>, <em class="rfc2119" title="not recommended">not recommended</em>, <em class="rfc2119" title="may">may</em>, and <em class="rfc2119" title="optional">optional</em> in this Recommendation have the meaning defined in [<cite><a class="bibref" href="#bib-RFC2119">RFC2119</a></cite>].</p>

</section>

<section class="normative" id="basic-concepts">

<!--OddPage-->
<h2><span class="secno">5. </span>Basic Concepts</h2>

<section id="the-context">
<h3><span class="secno">5.1 </span>The Context</h3>

<p>In JSON-LD, a <dfn title="context" id="dfn-context">context</dfn> is used to map <a class="tref internalDFN" title="term" href="#dfn-term">terms</a>, i.e., properties with associated
  values in an JSON document, to <a class="tref internalDFN" title="iri" href="#dfn-iri">IRIs</a>.</p>
<p>The Web uses <a class="tref internalDFN" title="iri" href="#dfn-iri">IRIs</a> for unambiguous identification. The
  idea is that these <a class="tref internalDFN" title="term" href="#dfn-term">terms</a> mean something that may be of use to other developers and that it is useful to
  give them an unambiguous identifier. That is, it is useful for <a class="tref internalDFN" title="term" href="#dfn-term">terms</a> to expand to IRIs so that
  developers don't accidentally step on each other's <dfn title="vocabulary" id="dfn-vocabulary">vocabulary</dfn> terms and other resources. Furthermore, developers, and
  machines, are able to use this <a class="tref internalDFN" title="iri" href="#dfn-iri"><abbr title="Internationalized Resource Identifier">IRI</abbr></a> (by plugging it directly into a web browser, for instance) to go to
  the term and get a definition of what the term means. This mechanism is analogous to the way we can use
  <a href="http://wordnet.princeton.edu/">WordNet</a> today to see the definition of words in the English language.
  Developers and machines need the same sort of definition of terms. <a class="tref internalDFN" title="iri" href="#dfn-iri">IRIs</a> provide a way to
  ensure that these terms are unambiguous. For example, the term <code>name</code> may
  map directly to the <abbr title="Internationalized Resource Identifier">IRI</abbr> <code>http://xmlns.com/foaf/0.1/name</code>. This allows JSON-LD documents to be constructed
  using the common JSON practice of simple key-value pairs while ensuring that the data is useful outside of the
  page, API or database in which it resides.</p>

<p>Note that, to avoid forward-compatibility issues, terms starting with an <code>@</code> character are to be avoided as they might be used as keywords in future versions of JSON-LD. Furthermore, the use of empty <a class="tref internalDFN" title="term" href="#dfn-term">terms</a> (<code>&quot;&quot;</code>)
  is discouraged as not all programming languages are able to handle empty
  property names.
</p>

<p>In a JSON-LD document, the mapping between <a class="tref internalDFN" title="term" href="#dfn-term">terms</a> and
  <a class="tref internalDFN" title="iri" href="#dfn-iri">IRIs</a> is typically collected in a <a class="tref internalDFN" title="context_definition" href="#dfn-context_definition">context definition</a>
  that would look something like this:</p>

<div class="example"><div class="example-title"><span>Example 1</span>: Context definition</div><pre class="example">{
  &quot;@context&quot;:
  {
    &quot;name&quot;: &quot;http://xmlns.com/foaf/0.1/name&quot;,
    &quot;depiction&quot;:
    {
      &quot;@id&quot;: &quot;http://xmlns.com/foaf/0.1/depiction&quot;,
      &quot;@type&quot;: &quot;@id&quot;
    },
    &quot;homepage&quot;:
    {
      &quot;@id&quot;: &quot;http://xmlns.com/foaf/0.1/homepage&quot;,
      &quot;@type&quot;: &quot;@id&quot;
    },
  }
}</pre></div>

<p>
Let's assume that a developer starts with the following JSON document:
</p>

<div class="example"><div class="example-title"><span>Example 2</span>: Sample JSON document</div><pre class="example">{
  &quot;name&quot;: &quot;Manu Sporny&quot;,
  &quot;homepage&quot;: &quot;http://manu.sporny.org/&quot;,
  &quot;depiction&quot;: &quot;http://twitter.com/account/profile_image/manusporny&quot;
}</pre></div>

<p>The developer can add a single line to the JSON document above
to reference the context and transform it into a JSON-LD document:</p>

<div class="example"><div class="example-title"><span>Example 3</span>: Referencing a JSON-LD context</div><pre class="example">{
  <span class="diff">&quot;@context&quot;: &quot;http://json-ld.org/contexts/person.jsonld&quot;,</span>
  &quot;name&quot;: &quot;Manu Sporny&quot;,
  &quot;homepage&quot;: &quot;http://manu.sporny.org/&quot;,
  &quot;depiction&quot;: &quot;http://twitter.com/account/profile_image/manusporny&quot;
}</pre></div>

<p>The additions above transform the previous JSON document into a JSON document
with added semantics because the <code>@context</code> specifies how the
<strong>name</strong>, <strong>homepage</strong>, and <strong>depiction</strong>
terms map to <a class="tref internalDFN" title="iri" href="#dfn-iri">IRIs</a>.
Mapping those keys to IRIs gives the data global context. If two
developers use the same <abbr title="Internationalized Resource Identifier">IRI</abbr> to describe a property, they are more than likely
expressing the same concept. This allows both developers to re-use each others'
data without having to agree to how their data will interoperate on a
site-by-site basis. Contexts may also contain type, language or additional information
for certain <a class="tref internalDFN" title="term" href="#dfn-term">terms</a>.</p>

<p>External JSON-LD context documents may contain extra information
located outside of the <code>@context</code> key, such as documentation about the
<a class="tref internalDFN" title="term" href="#dfn-term">terms</a> declared in the document. Information contained
outside of the <code>@context</code> value is simply discarded when the document
is used as an external JSON-LD context document
(see <a href="#referencing-contexts-from-json-documents" class="sec-ref"><span class="secno">6.4</span> <span class="sec-title">Referencing Contexts from JSON Documents</span></a>).</p>

<p>Contexts may also be specified in-line. This ensures that
  <a class="tref internalDFN" title="json-ld_document" href="#dfn-json-ld_document">JSON-LD documents</a> can be understood
  even in the absence of a connection to the Web.</p>

<div class="example"><div class="example-title"><span>Example 4</span>: In-line context definition</div><pre class="example">{
  <span class="diff">&quot;@context&quot;:
  {
    &quot;name&quot;: &quot;http://xmlns.com/foaf/0.1/name&quot;,
    &quot;depiction&quot;:
    {
      &quot;@id&quot;: &quot;http://xmlns.com/foaf/0.1/depiction&quot;,
      &quot;@type&quot;: &quot;@id&quot;
    },
    &quot;homepage&quot;:
    {
      &quot;@id&quot;: &quot;http://xmlns.com/foaf/0.1/homepage&quot;,
      &quot;@type&quot;: &quot;@id&quot;
    },
  },</span>
  &quot;name&quot;: &quot;Manu Sporny&quot;,
  &quot;homepage&quot;: &quot;http://manu.sporny.org/&quot;,
  &quot;depiction&quot;: &quot;http://twitter.com/account/profile_image/manusporny&quot;
}</pre></div>

<p>Contexts may be used at any time a <a class="tref internalDFN" title="node_object" href="#dfn-node_object">node object</a> is defined.
  In particular, a <a class="tref internalDFN" title="json-ld_document" href="#dfn-json-ld_document">JSON-LD document</a> may define more than one context,
  as in the following example:</p>
<div class="example"><div class="example-title"><span>Example 5</span>: Multiple separate contexts</div><pre class="example">[
  {
    <span class="diff">&quot;@context&quot;: &quot;http://example.org/contexts/person.jsonld&quot;,</span>
    &quot;name&quot;: &quot;Manu Sporny&quot;,
    &quot;homepage&quot;: &quot;http://manu.sporny.org/&quot;,
    &quot;depiction&quot;: &quot;http://twitter.com/account/profile_image/manusporny&quot;
  },
  {
    <span class="diff">&quot;@context&quot;: &quot;http://example.org/contexts/place.jsonld&quot;,</span>
    &quot;name&quot;: &quot;The Empire State Building&quot;,
    &quot;description&quot;: &quot;The Empire State Building is a 102-story landmark in New York City.&quot;,
    &quot;geo&quot;: {
      &quot;latitude&quot;: &quot;40.75&quot;,
      &quot;longitude&quot;: &quot;73.98&quot;
    }
  }
]</pre></div>

<p>This is useful when an author would like to use an existing context
  and add application-specific terms to the existing context. Duplicate context
  <a class="tref internalDFN" title="term" href="#dfn-term">terms</a> are overridden using a last-defined-overrides
  mechanism.</p>

<div class="example"><div class="example-title"><span>Example 6</span>: Scoped contexts within node objects</div><pre class="example">{
  <span class="diff">&quot;@context&quot;:
  {
    &quot;name&quot;: &quot;http://example.com/person#name&quot;,
    &quot;details&quot;: &quot;http://example.com/person#details&quot;
  },</span>
  &quot;<span class="diff">name</span>&quot;: &quot;Markus Lanthaler&quot;,
  ...
  &quot;details&quot;:
  {
    <span class="diff">&quot;@context&quot;: {
      &quot;name&quot;: &quot;http://example.com/organization#name&quot;
    },</span>
    &quot;<span class="diff">name</span>&quot;: &quot;Graz University of Technology&quot;
  }
}</pre></div>

<p>In the example above, the <code>name</code> prefix is overridden in the
  more deeply nested <code>details</code> structure. Note that this is
  rarely a good authoring practice and is typically used when there exist
  legacy applications that depend on the specific structure of the
  <a class="tref internalDFN" title="json_object" href="#dfn-json_object">JSON object</a>. If a <a class="tref internalDFN" title="term" href="#dfn-term">term</a> is re-defined within a
  context, all previous rules associated with the previous definition are
  removed. If that <a class="tref internalDFN" title="term" href="#dfn-term">term</a> is re-defined to <code>null</code>,
  the <a class="tref internalDFN" title="term" href="#dfn-term">term</a> is effectively removed from the list of
  <a class="tref internalDFN" title="term" href="#dfn-term">terms</a> defined in the <a class="tref internalDFN" title="active_context" href="#dfn-active_context">active context</a>.</p>

<p>A <a class="tref internalDFN" title="node_object" href="#dfn-node_object">node object</a> may specify multiple contexts, using an
  <a class="tref internalDFN" title="array" href="#dfn-array">array</a>, processed in order. The set of contexts defined within a specific <a class="tref internalDFN" title="node_object" href="#dfn-node_object">node object</a> are
  referred to as <dfn title="local_context" id="dfn-local_context">local contexts</dfn>. Setting the context to <code>null</code>
  effectively resets the <a class="tref internalDFN" title="active_context" href="#dfn-active_context">active context</a> to an empty context. The
  <dfn title="active_context" id="dfn-active_context">active context</dfn> refers to the accumulation of <a class="tref internalDFN" title="local_context" href="#dfn-local_context">local contexts</a>
  that are in scope at a specific point within the document. The following example
  specifies an external context and then layers a local context on top of the external
  context:</p>

<div class="example"><div class="example-title"><span>Example 7</span>: Combining external and local contexts</div><pre class="example">{
  <span class="diff">&quot;@context&quot;: [
    &quot;http://json-ld.org/contexts/person.jsonld&quot;,
    {
      &quot;pic&quot;: &quot;http://xmlns.com/foaf/0.1/depiction&quot;
    }
  ],</span>
  &quot;name&quot;: &quot;Manu Sporny&quot;,
  &quot;homepage&quot;: &quot;http://manu.sporny.org/&quot;,
  <span class="diff">&quot;pic&quot;: &quot;http://twitter.com/account/profile_image/manusporny&quot;</span>
}</pre></div>

<div class="note"><div class="note-title"><span>Note</span></div><p class="">To ensure the best possible performance, it is a best practice to
  put the <a class="tref internalDFN" title="context" href="#dfn-context">context</a> definition at the top of the JSON-LD document. If it isn't listed
  first, processors have to save each key-value pair until the <a class="tref internalDFN" title="context" href="#dfn-context">context</a> is processed.
  This creates a memory and complexity burden for certain types of
  low-memory footprint JSON-LD processors.</p></div>

</section>

<section id="from-json-to-json-ld">
  <h3><span class="secno">5.2 </span>From JSON to JSON-LD</h3>

  <p>If a set of <a class="tref internalDFN" title="term" href="#dfn-term">terms</a> such as, <strong>name</strong>,
    <strong>homepage</strong>, and <strong>depiction</strong>,
    are defined in a <a class="tref internalDFN" title="context" href="#dfn-context">context</a>, and that context is used to resolve the
    names in <a class="tref internalDFN" title="json_object" href="#dfn-json_object">JSON objects</a>, machines are able to automatically expand the terms to
    something unambiguous like this:</p>

  <div class="example"><div class="example-title"><span>Example 8</span>: Expanded terms</div><pre class="example">{
  &quot;<span class="diff">http://xmlns.com/foaf/0.1/name</span>&quot;: &quot;Manu Sporny&quot;,
  &quot;<span class="diff">http://xmlns.com/foaf/0.1/homepage</span>&quot;: &quot;http://manu.sporny.org&quot;
  &quot;<span class="diff">http://xmlns.com/foaf/0.1/depiction</span>&quot;: &quot;http://twitter.com/account/profile_image/manusporny&quot;
}</pre></div>

  <p>Doing this allows JSON to be unambiguously machine-readable without
    requiring developers to drastically change their workflow. A <a class="tref internalDFN" title="json_object" href="#dfn-json_object">JSON object</a>
     used to define property values of a <a class="tref internalDFN" title="node" href="#dfn-node">node</a> is called a <a class="tref internalDFN" title="node_object" href="#dfn-node_object">node object</a>.</p>

  <div class="note"><div class="note-title"><span>Note</span></div><p class="">The example above does not use the <code>@id</code> <a class="tref internalDFN" title="keyword" href="#dfn-keyword">keyword</a>
    to identify the node being described above. This type of node is called a
    <a class="tref internalDFN" title="blank_node" href="#dfn-blank_node">blank node</a>. It is advised that all <a class="tref internalDFN" title="node_object" href="#dfn-node_object">node objects</a>
    in JSON-LD are identified by <a class="tref internalDFN" title="iri" href="#dfn-iri">IRIs</a> via the <code>@id</code>
    keyword unless the data is not intended to be linked to from other data sets.</p></div>
</section>

<section id="iris">
<h3><span class="secno">5.3 </span>IRIs</h3>

<p><a class="tref internalDFN" title="iri" href="#dfn-iri">IRIs</a> (Internationalized Resource Identifiers) are fundamental to <a class="tref internalDFN" title="linked_data" href="#dfn-linked_data">Linked Data</a> as
  that is how most <a class="tref internalDFN" title="node" href="#dfn-node">nodes</a> and <a class="tref internalDFN" title="property" href="#dfn-property">properties</a>
  are identified. <a class="tref internalDFN" title="iri" href="#dfn-iri">IRIs</a> can be expressed in a variety of different ways in JSON-LD:</p>

<ol>
  <li>Except within a <a class="tref internalDFN" title="context" href="#dfn-context">context</a> definition, <a class="tref internalDFN" title="term" href="#dfn-term">terms</a> in the
    key position in a <a class="tref internalDFN" title="json_object" href="#dfn-json_object">JSON object</a> that have a mapping in the <a class="tref internalDFN" title="active_context" href="#dfn-active_context">active context</a> expand to an <a class="tref internalDFN" title="iri" href="#dfn-iri"><abbr title="Internationalized Resource Identifier">IRI</abbr></a>. If there's a <code>@vocab</code>
    mapping in the active context also <a class="tref internalDFN" title="term" href="#dfn-term">terms</a> without an explicit mapping
    in the active context are expanded to an <a class="tref internalDFN" title="iri" href="#dfn-iri"><abbr title="Internationalized Resource Identifier">IRI</abbr></a>.</li>
  <li>An <a class="tref internalDFN" title="iri" href="#dfn-iri"><abbr title="Internationalized Resource Identifier">IRI</abbr></a> is generated for the <a class="tref internalDFN" title="string" href="#dfn-string">string</a> value specified using
    <code>@id</code> or <code>@type</code>.</li>
  <li>An <a class="tref internalDFN" title="iri" href="#dfn-iri"><abbr title="Internationalized Resource Identifier">IRI</abbr></a> is generated for the <a class="tref internalDFN" title="string" href="#dfn-string">string</a> value of any key for which there
    are <a class="tref internalDFN" title="coercion" href="#dfn-coercion">coercion</a> rules in effect that identify the value as an <code>@id</code>.</li>
</ol>

<p>IRIs may be represented as an <a class="tref internalDFN" title="absolute_iri" href="#dfn-absolute_iri">absolute <abbr title="Internationalized Resource Identifier">IRI</abbr></a> or a <a class="tref internalDFN" title="relative_iri" href="#dfn-relative_iri">relative <abbr title="Internationalized Resource Identifier">IRI</abbr></a>.</p>

<p>An <dfn title="absolute_iri" id="dfn-absolute_iri">absolute <abbr title="Internationalized Resource Identifier">IRI</abbr></dfn> is defined in [<cite><a class="bibref" href="#bib-RFC3987">RFC3987</a></cite>] containing a <em>scheme</em> along with
  <em>path</em> and optional <em>query</em> and <em>fragment</em> segments. A <dfn title="relative_iri" id="dfn-relative_iri">relative <abbr title="Internationalized Resource Identifier">IRI</abbr></dfn> is an <abbr title="Internationalized Resource Identifier">IRI</abbr>
  that is relative to some other <a class="tref internalDFN" title="absolute_iri" href="#dfn-absolute_iri">absolute <abbr title="Internationalized Resource Identifier">IRI</abbr></a>. In JSON-LD all <a class="tref internalDFN" title="relative_iri" href="#dfn-relative_iri">relative IRIs</a> are resolved relative to the
  <dfn title="base_iri" id="dfn-base_iri">base <abbr title="Internationalized Resource Identifier">IRI</abbr></dfn> associated with the document (typically, the directory that contains the document or the document itself).</p>

<p>IRIs can be expressed directly in the key position like so:</p>

<div class="example"><div class="example-title"><span>Example 9</span>: IRI as a key</div><pre class="example">{
...
  &quot;<span class="diff">http://xmlns.com/foaf/0.1/name</span>&quot;: &quot;Manu Sporny&quot;,
...
}</pre></div>

<p>In the example above, the key <code>http://xmlns.com/foaf/0.1/name</code> is interpreted
  as an <a class="tref internalDFN" title="iri" href="#dfn-iri"><abbr title="Internationalized Resource Identifier">IRI</abbr></a> because it contains a colon
  (<code>:</code>) and the 'http' <a class="tref internalDFN" title="prefix" href="#dfn-prefix">prefix</a> does not exist in
  the context.</p>

<p>Term expansion occurs for IRIs if the value matches a <a class="tref internalDFN" title="term" href="#dfn-term">term</a> defined within the
<a class="tref internalDFN" title="active_context" href="#dfn-active_context">active context</a>:</p>

<div class="example"><div class="example-title"><span>Example 10</span>: Term expansion from context definition</div><pre class="example">{
  &quot;<span class="diff">@context</span>&quot;:
  {
    &quot;<span class="diff">name</span>&quot;: &quot;<span class="diff">http://xmlns.com/foaf/0.1/name</span>&quot;
...
  },
  &quot;<span class="diff">name</span>&quot;: &quot;Manu Sporny&quot;,
  &quot;status&quot;: &quot;trollin'&quot;,
...
}</pre></div>

<p><a class="tref internalDFN" title="term" href="#dfn-term">Terms</a> are case sensitive.</p>

<p>JSON keys that do not expand to an absolute <abbr title="Internationalized Resource Identifier">IRI</abbr> are ignored, or removed
in some cases, by the [<cite><a class="bibref" href="#bib-JSON-LD-API">JSON-LD-API</a></cite>]. However, JSON keys that do not include
a mapping in the <a class="tref internalDFN" title="context" href="#dfn-context">context</a> are still considered valid expressions
in JSON-LD documents - the keys just don't expand to unambiguous identifiers.</p>

<p><a class="tref internalDFN" title="prefix" href="#dfn-prefix">Prefixes</a> are expanded when the form of the value is a
  <a class="tref internalDFN" title="compact_iri" href="#dfn-compact_iri">compact <abbr title="Internationalized Resource Identifier">IRI</abbr></a> represented as a <code>prefix:suffix</code>
  combination, and the prefix matches a <a class="tref internalDFN" title="term" href="#dfn-term">term</a> defined within the
  <a class="tref internalDFN" title="active_context" href="#dfn-active_context">active context</a>:</p>

<div class="example"><div class="example-title"><span>Example 11</span>: Prefix expansion</div><pre class="example">{
  &quot;<span class="diff">@context</span>&quot;:
  {
    &quot;<span class="diff">foaf</span>&quot;: &quot;<span class="diff">http://xmlns.com/foaf/0.1/</span>&quot;
...
  },
  &quot;<span class="diff">foaf:name</span>&quot;: &quot;Manu Sporny&quot;,
...
}</pre></div>

<p><code>foaf:name</code> above will automatically expand out to the <abbr title="Internationalized Resource Identifier">IRI</abbr>
<code>http://xmlns.com/foaf/0.1/name</code>. See <a href="#compact-iris" class="sec-ref"><span class="secno">6.1</span> <span class="sec-title">Compact IRIs</span></a> for more details.</p>

<p>It is often common that all types and properties come from the same vocabulary. JSON-LD's
  <code>@vocab</code> keyword allows to set a common prefix to be used for all properties and types
  that neither match a <a class="tref internalDFN" title="term" href="#dfn-term">term</a> nor a <a class="tref internalDFN" title="compact_iri" href="#dfn-compact_iri">compact <abbr title="Internationalized Resource Identifier">IRI</abbr></a> or an <a class="tref internalDFN" title="absolute_iri" href="#dfn-absolute_iri">absolute <abbr title="Internationalized Resource Identifier">IRI</abbr></a>
  (i.e., do not contain a colon).</p>

<div class="example"><div class="example-title"><span>Example 12</span>: Using a common vocabulary prefix</div><pre class="example">{
  <span class="diff">&quot;@context&quot;: {
    &quot;@vocab&quot;: &quot;http://xmlns.com/foaf/1.0/&quot;
  },</span>
  &quot;@type&quot;: <span class="diff">&quot;Person&quot;</span>,
  <span class="diff">&quot;name&quot;</span>: &quot;Manu Sporny&quot;,
}</pre></div>

<p>An <a class="tref internalDFN" title="iri" href="#dfn-iri"><abbr title="Internationalized Resource Identifier">IRI</abbr></a> is generated when a <a class="tref internalDFN" title="json_object" href="#dfn-json_object">JSON object</a> is used in the
  value position that contains an <code>@id</code> keyword:</p>

<div class="example"><div class="example-title"><span>Example 13</span>: Expanded IRI definition</div><pre class="example">{
...
  &quot;homepage&quot;: { &quot;<span class="diff">@id</span>&quot;: &quot;http://manu.sporny.org&quot; }
...
}</pre></div>

<p>Specifying a <a class="tref internalDFN" title="json_object" href="#dfn-json_object">JSON object</a> with an
  <code>@id</code> key is used to identify that <a class="tref internalDFN" title="node" href="#dfn-node">node</a> using an
  <a class="tref internalDFN" title="iri" href="#dfn-iri"><abbr title="Internationalized Resource Identifier">IRI</abbr></a>. When the object has only the <code>@id</code>, it
  is called a <a class="tref internalDFN" title="node_object" href="#dfn-node_object">node object</a>. This facility may also be used to link to another
  <a class="tref internalDFN" title="node_object" href="#dfn-node_object">node object</a> using a mechanism called
  <a class="tref internalDFN" title="embedding" href="#dfn-embedding">embedding</a>, which is covered in the section titled
  <a href="#embedding" class="sec-ref"><span class="secno">6.10</span> <span class="sec-title">Embedding</span></a>.</p>

<p>If type <a class="tref internalDFN" title="coercion" href="#dfn-coercion">coercion</a> rules are specified in the <code>@context</code> for
a particular <a class="tref internalDFN" title="term" href="#dfn-term">term</a> or property <abbr title="Internationalized Resource Identifier">IRI</abbr>, an <abbr title="Internationalized Resource Identifier">IRI</abbr> is generated:</p>

<div class="example"><div class="example-title"><span>Example 14</span>: Type coercion</div><pre class="example">{<span class="diff">
  &quot;@context&quot;:
  {
    ...
    &quot;homepage&quot;:
    {
      &quot;@id&quot;: &quot;http://xmlns.com/foaf/0.1/homepage&quot;,
      &quot;@type&quot;: &quot;@id&quot;
    }
    ...
  }</span>
...
  &quot;homepage&quot;: &quot;http://manu.sporny.org/&quot;,
...
}</pre></div>

<p>In the example above, even though the value
<code>http://manu.sporny.org/</code> is expressed as a JSON
<a class="tref internalDFN" title="string" href="#dfn-string">string</a>, the type <a class="tref internalDFN" title="coercion" href="#dfn-coercion">coercion</a> rules will transform
the value into an <abbr title="Internationalized Resource Identifier">IRI</abbr> when generating the <a class="tref internalDFN" title="json-ld_graph" href="#dfn-json-ld_graph">JSON-LD graph</a>.</p>

</section>

<section id="node-identifiers">
<h3><span class="secno">5.4 </span>Node Identifiers</h3>

<p>To be able to externally reference nodes in a graph, it is important that each <a class="tref internalDFN" title="node" href="#dfn-node">node</a> has
  an unambiguous identifier. <a class="tref internalDFN" title="iri" href="#dfn-iri">IRIs</a> are a fundamental concept of
  <a class="tref internalDFN" title="linked_data" href="#dfn-linked_data">Linked Data</a>, and nodes should have a de-referencable
  identifier used to name and locate them. For nodes to be truly linked,
  de-referencing the identifier should result in a representation of that node
  (for example, using a URL to retrieve a web page).
  Associating an <abbr title="Internationalized Resource Identifier">IRI</abbr> with a node tells an application that the returned
  document contains a description of the node requested.</p>

<p>JSON-LD documents may also contain descriptions of other nodes, so it is necessary to be able to
  uniquely identify each node which may be externally referenced.</p>

<p>The node of a <a class="tref internalDFN" title="json_object" href="#dfn-json_object">JSON object</a> is identified using the <code>@id</code>
  <a class="tref internalDFN" title="keyword" href="#dfn-keyword">keyword</a>:</p>

<div class="example"><div class="example-title"><span>Example 15</span>: Identifying a node</div><pre class="example">{
  &quot;@context&quot;:
  {
    ...
    &quot;homepage&quot;:
    {
      &quot;@id&quot;: &quot;http://xmlns.com/foaf/0.1/homepage&quot;,
      &quot;@type&quot;: &quot;@id&quot;
    }
    ...
  },
  &quot;<span class="diff">@id</span>&quot;: &quot;<span class="diff">http://example.org/people#joebob</span>&quot;,
  &quot;homepage&quot;: &quot;http://manu.sporny.org/&quot;,
...
}</pre></div>

<p>The example above contains a <a class="tref internalDFN" title="node_object" href="#dfn-node_object">node object</a> identified by the <abbr title="Internationalized Resource Identifier">IRI</abbr>
  <code>http://example.org/people#joebob</code>.</p>

<p>Once defined, the <a class="tref internalDFN" title="node" href="#dfn-node">node</a>'s unique identifier can be used to refer to
  it from other parts of the document or from external documents, using
  a <a class="tref internalDFN" title="node_object" href="#dfn-node_object">node object</a> that only contains an <code>@id</code> key:</p>

<div class="example"><div class="example-title"><span>Example 16</span>: Referencing a node using its unique identifier</div><pre class="example">{
  &quot;@context&quot;: ...,
  &quot;@graph&quot;: [
    {
      &quot;@id&quot;: &quot;http://example.org/library&quot;,
      &quot;@type&quot;: &quot;ex:Library&quot;,
      <span class="diff">&quot;ex:contains&quot;: {&quot;@id&quot;: &quot;http://example.org/library/the-republic&quot;}</span>
    }, {
      &quot;@id&quot;: &quot;http://example.org/library/the-republic&quot;,
      &quot;@type&quot;: &quot;ex:Book&quot;,
      &quot;dc:creator&quot;: &quot;Plato&quot;,
      &quot;dc:title&quot;: &quot;The Republic&quot;,
      <span class="diff">&quot;ex:contains&quot;: {&quot;@id&quot;: &quot;http://example.org/library/the-republic#introduction&quot;}</span>
    }, {
      &quot;@id&quot;: &quot;http://example.org/library/the-republic#introduction&quot;,
      &quot;@type&quot;: &quot;ex:Chapter&quot;,
      &quot;dc:description&quot;: &quot;An introductory chapter on The Republic.&quot;,
      &quot;dc:title&quot;: &quot;The Introduction&quot;
    }
  ]
}
}</pre></div>

</section>

<section id="specifying-the-type">
<h3><span class="secno">5.5 </span>Specifying the Type</h3>

<p>The type of a particular node can be specified using the <code>@type</code>
  <a class="tref internalDFN" title="keyword" href="#dfn-keyword">keyword</a>. In <a class="tref internalDFN" title="linked_data" href="#dfn-linked_data">Linked Data</a>, types are uniquely
  identified with an <a class="tref internalDFN" title="iri" href="#dfn-iri"><abbr title="Internationalized Resource Identifier">IRI</abbr></a>.</p>

<div class="example"><div class="example-title"><span>Example 17</span>: Specifying the type for a node</div><pre class="example">{
...
  &quot;@id&quot;: &quot;http://example.org/people#joebob&quot;,
  &quot;<span class="diff">@type</span>&quot;: &quot;<span class="diff">http://xmlns.com/foaf/0.1/Person</span>&quot;,
...
}</pre></div>

<p>A node can be assigned more than one type by using the following markup
pattern:</p>

<div class="example"><div class="example-title"><span>Example 18</span>: Specifying multiple types for a node</div><pre class="example">{
...
  &quot;@id&quot;: &quot;http://example.org/places#BrewEats&quot;,
  &quot;<span class="diff">@type</span>&quot;: <span class="diff">[&quot;http://schema.org/Restaurant&quot;, &quot;http://schema.org/Brewery&quot;]</span>
...
}</pre></div>

<p>The value of a <code>@type</code> key may also be a <a class="tref internalDFN" title="term" href="#dfn-term">term</a> defined in the <a class="tref internalDFN" title="active_context" href="#dfn-active_context">active context</a>:</p>
<div class="example"><div class="example-title"><span>Example 19</span>: Using a term to specify the type</div><pre class="example">{
  &quot;@context&quot;: &quot;http://json-ld.org/contexts/person.jsonld&quot;,
  &quot;@id&quot;: &quot;http://manu.sporny.org/i/public&quot;,
  <span class="diff">&quot;@type&quot;: &quot;Person&quot;</span>,
  &quot;name&quot;: &quot;Manu Sporny&quot;,
  &quot;homepage&quot;: &quot;http://manu.sporny.org/&quot;,
  &quot;depiction&quot;: &quot;http://twitter.com/account/profile_image/manusporny&quot;
}</pre></div>

</section>

<section id="string-internationalization">
<h3><span class="secno">5.6 </span>String Internationalization</h3>

<p>At times, it is important to annotate a <a class="tref internalDFN" title="string" href="#dfn-string">string</a>
  with its language. In JSON-LD this is possible in a variety of ways.
  Firstly, it is possible to define a default language for a JSON-LD document
  by setting the <code>@language</code> key in the <code>@context</code> or in a
  <a class="tref internalDFN" title="term" href="#dfn-term">term</a> definition:</p>

<div class="example"><div class="example-title"><span>Example 20</span>: Setting the default language of a JSON-LD document</div><pre class="example">{
  <span class="diff">&quot;@context&quot;:
  {
    ...
    &quot;@language&quot;: &quot;ja&quot;
  },</span>
  &quot;name&quot;: <span class="diff">&quot;花澄&quot;</span>,
  &quot;occupation&quot;: <span class="diff">&quot;科学者&quot;</span>
}</pre></div>

<p>The example above would associate the <code>ja</code> language
  code with the two <a class="tref internalDFN" title="string" href="#dfn-string">strings</a> <em>花澄</em> and <em>科学者</em>.
  Languages codes are defined in [<cite><a class="bibref" href="#bib-BCP47">BCP47</a></cite>].</p>

<p>It is possible to override the default language by using an <a class="tref internalDFN" title="expanded_value" href="#dfn-expanded_value">expanded value</a>:</p>

<div class="example"><div class="example-title"><span>Example 21</span>: Overriding default language using an expanded value</div><pre class="example">{
  &quot;@context&quot;: {
    ...
    &quot;@language&quot;: &quot;ja&quot;
  },
  &quot;name&quot;: &quot;花澄&quot;,
  &quot;occupation&quot;: <span class="diff">{
    &quot;@value&quot;: &quot;Scientist&quot;,
    &quot;@language&quot;: &quot;en&quot;
  }</span>
}</pre></div>

<p>It is also possible to override the default language or specify a plain
value by omitting the <code>@language</code> tag or setting it to
<code>null</code> when expressing the <a class="tref internalDFN" title="expanded_value" href="#dfn-expanded_value">expanded value</a>:</p>

<div class="example"><div class="example-title"><span>Example 22</span>: Removing language information using an expanded value</div><pre class="example">{
  &quot;@context&quot;: {
    ...
    &quot;@language&quot;: &quot;ja&quot;
  },
  &quot;name&quot;: <span class="diff">{
    &quot;@value&quot;: &quot;Frank&quot;
  },</span>
  &quot;occupation&quot;: <span class="diff"> {
    &quot;@value&quot;: &quot;Ninja&quot;,
    &quot;@language&quot;: &quot;en&quot;
  }</span>,
  &quot;speciality&quot;: &quot;手裏剣&quot;
}</pre></div>

<p>Please note that language associations can only be applied to plain
  literal <a class="tref internalDFN" title="string" href="#dfn-string">strings</a>. That is,
  <a class="tref internalDFN" title="typed_value" href="#dfn-typed_value">typed values</a> or values that are subject
  to <a href="#type-coercion" class="sec-ref"><span class="secno">6.6</span> <span class="sec-title">Type Coercion</span></a> cannot be language tagged.</p>

<p>To clear the default language for a subtree, <code>@language</code> can
be set to <code>null</code> in a <a class="tref internalDFN" title="local_context" href="#dfn-local_context">local context</a> as follows:</p>

<div class="example"><div class="example-title"><span>Example 23</span>: Clearing default language</div><pre class="example">{
  &quot;@context&quot;: {
    ...
    &quot;@language&quot;: &quot;ja&quot;
  },
  &quot;name&quot;: &quot;花澄&quot;,
  &quot;details&quot;: {
<span class="diff">    &quot;@context&quot;: {
      &quot;@language&quot;: null
    },</span>
    &quot;occupation&quot;: &quot;Ninja&quot;
  }
}</pre></div>

<div class="note"><div class="note-title"><span>Note</span></div><p class="">JSON-LD allows one to associate language information with
  <a class="tref internalDFN" title="term" href="#dfn-term">terms</a>. See <a href="#expanded-term-definition" class="sec-ref"><span class="secno">6.5</span> <span class="sec-title">Expanded Term Definition</span></a> for
  more details.</p></div>

</section>

<section id="json-ld-syntax">
  <h3><span class="secno">5.7 </span>JSON-LD Syntax</h3>

  <p>A <a class="tref internalDFN" title="json-ld_document" href="#dfn-json-ld_document">JSON-LD document</a> is first, and foremost, a JSON document
    (as defined in [<cite><a class="bibref" href="#bib-RFC4627">RFC4627</a></cite>]). However, JSON-LD
    describes a specific syntax to use for expressing Linked Data. This
    includes the use of specific keywords, as identified in <a href="#syntax-tokens-and-keywords" class="sec-ref"><span class="secno">3.2</span> <span class="sec-title">Syntax Tokens and Keywords</span></a> for
    expressing <a title="node object">node objects</a>, values,
    and the <a href="#dfn-context" class="internalDFN">context</a>. See <a href="#json-ld-grammar" class="sec-ref"><span class="secno">B.</span> <span class="sec-title">JSON-LD Grammar</span></a> for authoring
    guidelines.</p>

</section>
</section>

<section id="advanced-concepts">

<!--OddPage-->
<h2><span class="secno">6. </span>Advanced Concepts</h2>

<em>This section is normative.</em>

<p>JSON-LD has a number of features that provide functionality above and beyond
the core functionality described above. The following section describes this
advanced functionality in more detail.
</p>

<section id="compact-iris">
  <h3><span class="secno">6.1 </span>Compact IRIs</h3>
  <p>
    <a class="tref internalDFN" title="term" href="#dfn-term">Terms</a> in <a class="tref internalDFN" title="linked_data" href="#dfn-linked_data">Linked Data</a> documents may draw from
    a number of different <a class="tref internalDFN" title="vocabulary" href="#dfn-vocabulary">vocabularies</a>.
    At times, declaring every single <a class="tref internalDFN" title="term" href="#dfn-term">term</a> that a document uses can require the
    developer to declare tens, if not hundreds of potential
    <a class="tref internalDFN" title="vocabulary" href="#dfn-vocabulary">vocabulary</a> <a class="tref internalDFN" title="term" href="#dfn-term">terms</a> that are used across an
    application. This is a concern for at least two reasons: the
    first is the cognitive load on the developer of remembering all of the
    <a class="tref internalDFN" title="term" href="#dfn-term">terms</a>, and the second is the serialized size of the
    <a class="tref internalDFN" title="context" href="#dfn-context">context</a> if it is specified inline. In order to address these issues,
    the concept of a <a class="tref internalDFN" title="compact_iri" href="#dfn-compact_iri">compact <abbr title="Internationalized Resource Identifier">IRI</abbr></a> is introduced.</p>
  <p>
    A <dfn title="compact_iri" id="dfn-compact_iri">compact <abbr title="Internationalized Resource Identifier">IRI</abbr></dfn> is a way of expressing an <a class="tref internalDFN" title="iri" href="#dfn-iri"><abbr title="Internationalized Resource Identifier">IRI</abbr></a>
    using a <em>prefix</em> and <em>suffix</em> separated by a colon (<code>:</code>) which is
    similar to the <cite><a href="http://www.w3.org/TR/rdfa-core/#s_curies">CURIE Syntax</a></cite>
    in [<cite><a class="bibref" href="#bib-RDFA-CORE">RDFA-CORE</a></cite>]. The <dfn title="prefix" id="dfn-prefix">prefix</dfn> is a <a class="tref internalDFN" title="term" href="#dfn-term">term</a> taken from the
    <a class="tref internalDFN" title="active_context" href="#dfn-active_context">active context</a> and is a short string identifying a
    particular <a class="tref internalDFN" title="iri" href="#dfn-iri"><abbr title="Internationalized Resource Identifier">IRI</abbr></a> in a JSON-LD document.
    For example, the prefix <code>foaf</code> may be used as a short
    hand for the Friend-of-a-Friend vocabulary, which is identified using
    the <abbr title="Internationalized Resource Identifier">IRI</abbr> <code>http://xmlns.com/foaf/0.1/</code>. A developer may append
    any of the FOAF <a class="tref internalDFN" title="vocabulary" href="#dfn-vocabulary">vocabulary</a> terms to the end of the prefix
    to specify a short-hand version of the <a class="tref internalDFN" title="absolute_iri" href="#dfn-absolute_iri">absolute <abbr title="Internationalized Resource Identifier">IRI</abbr></a> for the
    <a class="tref internalDFN" title="vocabulary" href="#dfn-vocabulary">vocabulary</a> term. For example, <code>foaf:name</code> would
    be expanded out to the <abbr title="Internationalized Resource Identifier">IRI</abbr> <code>http://xmlns.com/foaf/0.1/name</code>.
    Instead of having to remember and type out the entire <abbr title="Internationalized Resource Identifier">IRI</abbr>, the developer
    can instead use the prefix in their JSON-LD markup.
  </p>
  <p>Terms are interpreted as <a class="tref internalDFN" title="compact_iri" href="#dfn-compact_iri">compact IRIs</a> if they contain at least one
    colon and the first colon is not followed by two slashes (<code>//</code>, as in
    <code>http://example.com</code>). To generate the full <a class="tref internalDFN" title="iri" href="#dfn-iri"><abbr title="Internationalized Resource Identifier">IRI</abbr></a>,
    the value is first split into a <em>prefix</em> and <em>suffix</em> at the first
    occurrence of a colon (<code>:</code>). If the <a class="tref internalDFN" title="active_context" href="#dfn-active_context">active context</a>
    contains a term mapping for <em>prefix</em>, an <abbr title="Internationalized Resource Identifier">IRI</abbr> is generated by
    prepending the mapped <em>prefix</em> to the (possibly empty) <em>suffix</em>
    using textual concatenation.  If no prefix mapping is defined, the value is interpreted
    as an <a class="tref internalDFN" title="absolute_iri" href="#dfn-absolute_iri">absolute <abbr title="Internationalized Resource Identifier">IRI</abbr></a>. If the prefix is an underscore
    (<code>_</code>), the <abbr title="Internationalized Resource Identifier">IRI</abbr> remains unchanged.
  </p>
  <p>Consider the following example:</p>
  <div class="example"><div class="example-title"><span>Example 24</span>: Compact IRIs</div><pre class="example">{
  &quot;@context&quot;:
  {
    <span class="diff">&quot;dc&quot;: &quot;http://purl.org/dc/elements/1.1/&quot;,</span>
    <span class="diff">&quot;ex&quot;: &quot;http://example.org/vocab#&quot;</span>
  },
  &quot;@id&quot;: &quot;http://example.org/library&quot;,
  &quot;@type&quot;: <span class="diff">&quot;ex:Library&quot;</span>,
  <span class="diff">&quot;ex:contains&quot;</span>:
  {
    &quot;@id&quot;: &quot;http://example.org/library/the-republic&quot;,
    &quot;@type&quot;: <span class="diff">&quot;ex:Book&quot;</span>,
    <span class="diff">&quot;dc:creator&quot;</span>: &quot;Plato&quot;,
    <span class="diff">&quot;dc:title&quot;</span>: &quot;The Republic&quot;,
    <span class="diff">&quot;ex:contains&quot;</span>:
    {
      &quot;@id&quot;: &quot;http://example.org/library/the-republic#introduction&quot;,
      &quot;@type&quot;: <span class="diff">&quot;ex:Chapter&quot;</span>,
      <span class="diff">&quot;dc:description&quot;</span>: &quot;An introductory chapter on The Republic.&quot;,
      <span class="diff">&quot;dc:title&quot;</span>: &quot;The Introduction&quot;
    }
  }
}</pre></div>
  <p>
    In this example, two different <a class="tref internalDFN" title="vocabulary" href="#dfn-vocabulary">vocabularies</a>
    are referred to using prefixes. Those prefixes are then used as type and
    property values using the compact <abbr title="Internationalized Resource Identifier">IRI</abbr> <code>prefix:suffix</code> notation.
  </p>
  <p>It's also possible to use compact IRIs within the context as shown in the
    following example:</p>
  <div class="example"><div class="example-title"><span>Example 25</span>: Using vocabularies</div><pre class="example">{
  &quot;@context&quot;:
  {
    &quot;xsd&quot;: &quot;http://www.w3.org/2001/XMLSchema#&quot;,
    &quot;foaf&quot;: &quot;http://xmlns.com/foaf/0.1/&quot;,
    <span class="diff">&quot;foaf:homepage&quot;</span>: { &quot;@type&quot;: &quot;@id&quot; },
    &quot;picture&quot;: { &quot;@id&quot;: <span class="diff">&quot;foaf:depiction&quot;</span>, &quot;@type&quot;: &quot;@id&quot; }
  },
  &quot;@id&quot;: &quot;http://me.markus-lanthaler.com/&quot;,
  &quot;@type&quot;: &quot;foaf:Person&quot;,
  &quot;foaf:name&quot;: &quot;Markus Lanthaler&quot;,
  &quot;foaf:homepage&quot;: &quot;http://www.markus-lanthaler.com/&quot;,
  &quot;picture&quot;: &quot;http://twitter.com/account/profile_image/markuslanthaler&quot;
}</pre></div>
</section>

<section id="typed-values">
<h3><span class="secno">6.2 </span>Typed Values</h3>

<p>
  A value with an associated type, also known as a
  <a class="tref internalDFN" title="typed_value" href="#dfn-typed_value">typed value</a>, is indicated by associating a value with
  an <a class="tref internalDFN" title="iri" href="#dfn-iri"><abbr title="Internationalized Resource Identifier">IRI</abbr></a> which indicates the value's type. Typed values may be
  expressed in JSON-LD in three ways:
</p>

<ol>
  <li>By utilizing the <code>@type</code> <a class="tref internalDFN" title="keyword" href="#dfn-keyword">keyword</a> when defining
    a <a class="tref internalDFN" title="term" href="#dfn-term">term</a> within a <code>@context</code> section.</li>
  <li>By utilizing an <a class="tref internalDFN" title="expanded_typed_value" href="#dfn-expanded_typed_value">expanded typed value</a>.</li>
  <li>By using a native JSON type such as <a class="tref internalDFN" title="number" href="#dfn-number">number</a>, <a class="tref internalDFN" title="true" href="#dfn-true">true</a>, or <a class="tref internalDFN" title="false" href="#dfn-false">false</a>.</li>
</ol>

<p>The first example uses the <code>@type</code> keyword to associate a
type with a particular <a class="tref internalDFN" title="term" href="#dfn-term">term</a> in the <code>@context</code>:</p>

<div class="example"><div class="example-title"><span>Example 26</span>: Expanded term definition with type coercion</div><pre class="example">{
  <span class="diff">&quot;@context&quot;:
  {
    &quot;modified&quot;:
    {
      &quot;@id&quot;: &quot;http://purl.org/dc/terms/modified&quot;,
      &quot;@type&quot;: &quot;http://www.w3.org/2001/XMLSchema#dateTime&quot;
    }
  },</span>
...
  &quot;modified&quot;: &quot;2010-05-29T14:17:39+02:00&quot;,
...
}</pre></div>

<p>The <em>modified</em> key's value above is automatically type coerced to a
datetime value because of the information specified in the
<code>@context</code>.</p>

<p>The second example uses the expanded form of setting the type information
in the body of a JSON-LD document:</p>

<div class="example"><div class="example-title"><span>Example 27</span>: Expanded value with type</div><pre class="example">{
  &quot;@context&quot;:
  {
    &quot;modified&quot;:
    {
      &quot;@id&quot;: &quot;http://purl.org/dc/terms/modified&quot;
    }
  },
...
  &quot;modified&quot;:
  <span class="diff">{
    &quot;@value&quot;: &quot;2010-05-29T14:17:39+02:00&quot;,
    &quot;@type&quot;: &quot;http://www.w3.org/2001/XMLSchema#dateTime&quot;
  }</span>
...
}</pre></div>

<p>Both examples above would generate the value
  <code>2010-05-29T14:17:39+02:00</code> with the type
  <code>http://www.w3.org/2001/XMLSchema#dateTime</code>. Note that it is
  also possible to use a <a class="tref internalDFN" title="term" href="#dfn-term">term</a> or a <a class="tref internalDFN" title="compact_iri" href="#dfn-compact_iri">compact <abbr title="Internationalized Resource Identifier">IRI</abbr></a> to
  express the value of a type.</p>

<p>The <code>@type</code> <a class="tref internalDFN" title="keyword" href="#dfn-keyword">keyword</a> is also used to associate a type
  with a <a class="tref internalDFN" title="node" href="#dfn-node">node</a>. The concept of a <dfn title="node_type" id="dfn-node_type">node type</dfn> and
  a <dfn title="value_type" id="dfn-value_type">value type</dfn> are different. This is similar to object-oriented
  programming languages where both scalar and structured types use the same
  class inheritance mechanism, even though scalar types and structured types are
  inherently different.</p>

<div class="example"><div class="example-title"><span>Example 28</span>: Example demonstrating the context-sensitivity for @type</div><pre class="example">{
...
  &quot;@id&quot;: &quot;http://example.org/posts#TripToWestVirginia&quot;,
  <span class="diff">&quot;@type&quot;: &quot;http://schema.org/BlogPosting&quot;</span>,
  &quot;modified&quot;:
  {
    &quot;@value&quot;: &quot;2010-05-29T14:17:39+02:00&quot;,
    <span class="diff">&quot;@type&quot;: &quot;http://www.w3.org/2001/XMLSchema#dateTime&quot;</span>
  }
...
}</pre></div>

<p>The first use of <code>@type</code> associates a <a class="tref internalDFN" title="node_type" href="#dfn-node_type">node type</a>
  (<code>http://schema.org/BlogPosting</code>) with the <a class="tref internalDFN" title="node" href="#dfn-node">node</a>,
  which is expressed using the <code>@id</code> <a class="tref internalDFN" title="keyword" href="#dfn-keyword">keyword</a>.
  The second use of <code>@type</code> associates a <a class="tref internalDFN" title="value_type" href="#dfn-value_type">value type</a>
  (<code>http://www.w3.org/2001/XMLSchema#dateTime</code>) with the
  value expressed using the <code>@value</code> <a class="tref internalDFN" title="keyword" href="#dfn-keyword">keyword</a>. As a
  general rule, when <code>@value</code> and <code>@type</code> are used in
  the same <a class="tref internalDFN" title="json_object" href="#dfn-json_object">JSON object</a>, the <code>@type</code>
  <a class="tref internalDFN" title="keyword" href="#dfn-keyword">keyword</a> is expressing a <a class="tref internalDFN" title="value_type" href="#dfn-value_type">value type</a>.
  Otherwise, the <code>@type</code> <a class="tref internalDFN" title="keyword" href="#dfn-keyword">keyword</a> is expressing a
  <a class="tref internalDFN" title="node_type" href="#dfn-node_type">node type</a>.</p>

</section>

<section id="language-tagged-strings">
<h3><span class="secno">6.3 </span>Language-tagged Strings</h3>

<p>
  A string with an associated language, also known as a
  <a class="tref internalDFN" title="language-tagged_string" href="#dfn-language-tagged_string">language-tagged string</a>, is indicated by associating a string with
  a language code as defined in [<cite><a class="bibref" href="#bib-BCP47">BCP47</a></cite>]. Language-tagged strings may be
  expressed in JSON-LD in four ways:
</p>

<ol>
  <li>By defining a global language using the <code>@language</code>
    <a class="tref internalDFN" title="keyword" href="#dfn-keyword">keyword</a> within a <code>@context</code> section.</li>
  <li>By utilizing the <code>@language</code> <a class="tref internalDFN" title="keyword" href="#dfn-keyword">keyword</a> when defining
    a <a class="tref internalDFN" title="term" href="#dfn-term">term</a> within a <code>@context</code> section.</li>
  <li>By utilizing an <a class="tref internalDFN" title="expanded_language-tagged_string" href="#dfn-expanded_language-tagged_string">expanded language-tagged string</a>.</li>
  <li>By utilizing a <a class="tref internalDFN" title="language_map" href="#dfn-language_map">language map</a>, provided the underlying
    <code>term</code> is defined with a <code>@container</code>
    <a class="tref internalDFN" title="keyword" href="#dfn-keyword">keyword</a> whose value is <code>@language</code> within
    a <code>@context</code> section.</li>
</ol>

<p>The first example uses the <code>@language</code> keyword to associate a
type with a particular <a class="tref internalDFN" title="term" href="#dfn-term">term</a> in the <code>@context</code>:</p>

<div class="example"><div class="example-title"><span>Example 29</span>: Expanded term definition with language coercion</div><pre class="example">{
  <span class="diff">&quot;@context&quot;:
  {
    &quot;title&quot;:
    {
      &quot;@id&quot;: &quot;http://purl.org/dc/terms/title&quot;,
      &quot;@language&quot;: &quot;en&quot;
    }
  },</span>
...
  &quot;title&quot;: &quot;JSON-LD Syntax&quot;,
...
}</pre></div>

<p>The <em>modified</em> key's value above is automatically
  language coerced to a English value because of the information specified in
  the <code>@context</code>.</p>

<p>The second example uses the expanded form of setting the language information
in the body of a JSON-LD document:</p>

<div class="example"><div class="example-title"><span>Example 30</span>: Expanded value with language</div><pre class="example">{
  &quot;@context&quot;:
  {
    &quot;title&quot;:
    {
      &quot;@id&quot;: &quot;http://purl.org/dc/terms/title&quot;
    }
  },
...
  &quot;title&quot;:
  <span class="diff">{
    &quot;@value&quot;: &quot;JSON-LD Syntax&quot;,
    &quot;@language&quot;: &quot;en&quot;
  }</span>
...
}</pre></div>

<p>Both examples above would generate the value <code>JSON-LD Syntax</code>
  tagged with the language <code>en</code>; which is the [<cite><a class="bibref" href="#bib-BCP47">BCP47</a></cite>] code
  for the English language.</p>

<p>Systems that support multiple languages often need to express data values in
each language. Typically, such systems also try to ensure that developers have
a programatically easy way to navigate the datastructures for the
language-specific data. In this case, <a class="tref internalDFN" title="language_map" href="#dfn-language_map">language maps</a>
may be utilized.</p>

<div class="example"><div class="example-title"><span>Example 31</span>: Language map expressing a property in three languages</div><pre class="example">{
  &quot;@context&quot;:
  {
    &quot;title&quot;:
    {
      &quot;@id&quot;: &quot;http://purl.org/dc/terms/title&quot;,
      <span class="diff">&quot;@container&quot;: &quot;@language&quot;</span>
    }
  },
...
  &quot;title&quot;:
  <span class="diff">{
    &quot;en&quot;: &quot;JSON-LD Syntax&quot;,
    &quot;ru&quot;: &quot;JSON-LD Синтаксис&quot;,
    &quot;ja&quot;: &quot;JSON-LDの構文&quot;
  }</span>
...
}</pre></div>

<p>In the example above, the title is expressed in three languages; English,
  Russian, and Japanese. To access the data above in a programming language
  supporting dot-notation accessors for object properties, a developer may
  use the <code>property.language</code> pattern. For example, to access the
  Japanese version of the title, a developer would use the following code
  snippet: <code>obj.title.ja</code>.</p>
</section>

<section id="referencing-contexts-from-json-documents">
<h3><span class="secno">6.4 </span>Referencing Contexts from JSON Documents</h3>

<p>Ordinary JSON documents can be transformed into JSON-LD documents by referencing
to an external JSON-LD <a class="tref internalDFN" title="context" href="#dfn-context">context</a> in an HTTP Link Header. Doing this
allows JSON to be unambiguously machine-readable without requiring developers to
drastically change their workflow and provides an upgrade path for existing
infrastructure without breaking existing clients that rely on the <code>application/json</code>
media type.
</p>

<p>
In order to use an external context with an ordinary JSON document, an author
<em class="rfc2119" title="must">must</em> specify an <a class="tref internalDFN" title="iri" href="#dfn-iri"><abbr title="Internationalized Resource Identifier">IRI</abbr></a> to a valid <a class="tref internalDFN" title="json-ld_document" href="#dfn-json-ld_document">JSON-LD document</a> in an HTTP Link
Header [<cite><a class="bibref" href="#bib-RFC5988">RFC5988</a></cite>] using the <code>http://www.w3.org/ns/json-ld#context</code> link relation.

The referenced document <em class="rfc2119" title="must">must</em> have a top-level <a class="tref internalDFN" title="node_object" href="#dfn-node_object">node object</a>. The
<code>@context</code> subtree within that object is added to the top-level
<a class="tref internalDFN" title="node_object" href="#dfn-node_object">node object</a> of the referencing document. If an <a class="tref internalDFN" title="array" href="#dfn-array">array</a> is at the top-level of the
referencing document and its items are <a class="tref internalDFN" title="node_object" href="#dfn-node_object">node objects</a>, the <code>@context</code>
subtree is added to all <a class="tref internalDFN" title="array" href="#dfn-array">array</a> items. All extra information located outside
of the <code>@context</code> subtree in the referenced document <em class="rfc2119" title="must">must</em> be
discarded.
</p>

<p>The following example demonstrates the use of an external context with an
ordinary JSON document:</p>

<div class="example"><div class="example-title"><span>Example 32</span>: Specifing context through HTTP header</div><pre class="example">GET /ordinary-json-document.json HTTP/1.1
Host: example.com
Accept: application/ld+json,application/json,*/*;q=0.1

====================================

HTTP/1.0 200 OK
...
Content-Type: <span class="diff">application/json</span>
<span class="diff">Link: &lt;http://json-ld.org/contexts/person.jsonld&gt;; rel=&quot;http://www.w3.org/ns/json-ld#context&quot;; type=&quot;application/ld+json&quot;</span>

{
  &quot;name&quot;: &quot;Markus Lanthaler&quot;,
  &quot;homepage&quot;: &quot;http://www.markus-lanthaler.com/&quot;,
  &quot;depiction&quot;: &quot;http://twitter.com/account/profile_image/markuslanthaler&quot;
}</pre></div>

<p>Please note that <a class="tref internalDFN" title="json-ld_document" href="#dfn-json-ld_document">JSON-LD documents</a>
  served with the <code>application/ld+json</code>
  media type <em class="rfc2119" title="must">must</em> have all context information, including references to external
  contexts, within the body of the document. Contexts linked via a
  <code>http://www.w3.org/ns/json-ld#context</code> HTTP Link Header <em class="rfc2119" title="must">must</em> be
  ignored for such documents.</p>

</section>

<section id="expanded-term-definition">
<h3><span class="secno">6.5 </span>Expanded Term Definition</h3>

<p>Within a <a class="tref internalDFN" title="context" href="#dfn-context">context</a> definition, <a class="tref internalDFN" title="term" href="#dfn-term">terms</a> may be
   defined using an <a class="tref internalDFN" title="expanded_term_definition" href="#dfn-expanded_term_definition">expanded term definition</a> to allow for additional information
   associated with the <a class="tref internalDFN" title="term" href="#dfn-term">term</a> to be specified (see also
   <a href="#type-coercion" class="sec-ref"><span class="secno">6.6</span> <span class="sec-title">Type Coercion</span></a> and
   <a href="#sets-and-lists" class="sec-ref"><span class="secno">6.9</span> <span class="sec-title">Sets and Lists</span></a>).</p>

<p>Instead of using a string representation of an <abbr title="Internationalized Resource Identifier">IRI</abbr>, the <abbr title="Internationalized Resource Identifier">IRI</abbr> may be
specified using a <a class="tref internalDFN" title="json_object" href="#dfn-json_object">JSON object</a> having an <code>@id</code> key,
and a <a class="tref internalDFN" title="term" href="#dfn-term">term</a>, a <a class="tref internalDFN" title="compact_iri" href="#dfn-compact_iri">compact <abbr title="Internationalized Resource Identifier">IRI</abbr></a>, or an
<a class="tref internalDFN" title="absolute_iri" href="#dfn-absolute_iri">absolute <abbr title="Internationalized Resource Identifier">IRI</abbr></a> as value.</p>

<div class="example"><div class="example-title"><span>Example 33</span>: Expanded term definition</div><pre class="example">{
  &quot;@context&quot;:
  {
    &quot;foaf&quot;: <span class="diff">{ &quot;@id&quot;: &quot;http://xmlns.com/foaf/0.1/&quot; }</span>,
    &quot;name&quot;: <span class="diff">{ &quot;@id&quot;: &quot;http://xmlns.com/foaf/0.1/name&quot; }</span>,
    &quot;homepage&quot;: <span class="diff">{ &quot;@id&quot;: &quot;foaf:homepage&quot; }</span>,
    &quot;depiction&quot;: <span class="diff">{ &quot;@id&quot;: &quot;foaf:depiction&quot; }</span>
  },
  &quot;name&quot;: &quot;Manu Sporny&quot;,
  &quot;homepage&quot;: &quot;http://manu.sporny.org/&quot;,
  &quot;depiction&quot;: &quot;http://twitter.com/account/profile_image/manusporny&quot;
}</pre></div>

<p>This allows additional information to be associated with the term. This
  may be used for <a href="#type-coercion" class="sec-ref"><span class="secno">6.6</span> <span class="sec-title">Type Coercion</span></a>,
  <a href="#sets-and-lists" class="sec-ref"><span class="secno">6.9</span> <span class="sec-title">Sets and Lists</span></a>, or to associate language
  information with a <a class="tref internalDFN" title="term" href="#dfn-term">term</a> as shown in the following example:</p>

<div class="example"><div class="example-title"><span>Example 34</span>: Expanded term definition with language</div><pre class="example">{
  &quot;@context&quot;: {
    ...
    &quot;ex&quot;: &quot;http://example.com/&quot;,
    &quot;@language&quot;: &quot;ja&quot;,
    &quot;name&quot;: { &quot;@id&quot;: &quot;ex:name&quot;, <span class="diff">&quot;@language&quot;: null</span> },
    &quot;occupation&quot;: { &quot;@id&quot;: &quot;ex:occupation&quot; },
    &quot;occupation_en&quot;: { &quot;@id&quot;: &quot;ex:occupation&quot;, <span class="diff">&quot;@language&quot;: &quot;en&quot;</span> },
    &quot;occupation_cs&quot;: { &quot;@id&quot;: &quot;ex:occupation&quot;, <span class="diff">&quot;@language&quot;: &quot;cs&quot;</span> }
  },
  <span class="diff">&quot;name&quot;: &quot;Yagyū Muneyoshi&quot;,
  &quot;occupation&quot;: &quot;忍者&quot;,
  &quot;occupation_en&quot;: &quot;Ninja&quot;,
  &quot;occupation_cs&quot;: &quot;Nindža&quot;,</span>
  ...
}</pre></div>

<p>The example above would associate <em>忍者</em> with the specified default
  language code <code>ja</code>, <em>Ninja</em> with the language code
  <code>en</code>, and <em>Nindža</em> with the language code <code>cs</code>.
  The value of <code>name</code>, <em>Yagyū Muneyoshi</em> wouldn't be
  associated with any language code since <code>@language</code> was reset to
  <a class="tref internalDFN" title="null" href="#dfn-null">null</a> in the <a class="tref internalDFN" title="expanded_term_definition" href="#dfn-expanded_term_definition">expanded term definition</a>.</p>

<p>Expanded terms may also be defined using <a class="tref internalDFN" title="compact_iri" href="#dfn-compact_iri">compact IRIs</a> or
  <a class="tref internalDFN" title="absolute_iri" href="#dfn-absolute_iri">absolute IRIs</a> as keys. If the definition does not include an
  <code>@id</code> key, the expanded <abbr title="Internationalized Resource Identifier">IRI</abbr> is determined by performing expansion of the key
  within the current <a class="tref internalDFN" title="active_context" href="#dfn-active_context">active context</a>. This mechanism is mainly used to associate type or language
  information with a <a class="tref internalDFN" title="compact_iri" href="#dfn-compact_iri">compact <abbr title="Internationalized Resource Identifier">IRI</abbr></a> or an <a class="tref internalDFN" title="absolute_iri" href="#dfn-absolute_iri">absolute <abbr title="Internationalized Resource Identifier">IRI</abbr></a>.</p>

<div class="note"><div class="note-title"><span>Note</span></div><p class="">While it is possible to define a
  <a class="tref internalDFN" title="compact_iri" href="#dfn-compact_iri">compact <abbr title="Internationalized Resource Identifier">IRI</abbr></a>, or an absolute <abbr title="Internationalized Resource Identifier">IRI</abbr> to expand to some
  other unrelated <abbr title="Internationalized Resource Identifier">IRI</abbr> (for example, <code>foaf:name</code> expanding to
  <code>http://example.org/unrelated#species</code>),
  such usage is strongly discouraged.</p></div>
</section>

<section id="type-coercion">
<h3><span class="secno">6.6 </span>Type Coercion</h3>

<p>JSON-LD supports the coercion of values to particular data types.
Type <dfn title="coercion" id="dfn-coercion">coercion</dfn> allows someone deploying JSON-LD to coerce the incoming or
outgoing values to the proper data type based on a mapping of data type <a class="tref internalDFN" title="iri" href="#dfn-iri">IRIs</a> to
<a class="tref internalDFN" title="term" href="#dfn-term">terms</a>. Using type coercion, value representation is preserved without requiring
the data type to be specified with each piece of data.</p>

<p>Type coercion is specified within an <a href="#expanded-term-definition" class="sec-ref"><span class="secno">6.5</span> <span class="sec-title">Expanded Term Definition</span></a>
  using the <code>@type</code> key. The value of this key expands to an <a class="tref internalDFN" title="iri" href="#dfn-iri"><abbr title="Internationalized Resource Identifier">IRI</abbr></a>.
  Alternatively, the <a class="tref internalDFN" title="keyword" href="#dfn-keyword">keyword</a> <code>@id</code> may be used as value to indicate
  that within the body of a JSON-LD document, a string value of a <a class="tref internalDFN" title="term" href="#dfn-term">term</a> coerced to
  <code>@id</code> is to be interpreted as an <a class="tref internalDFN" title="iri" href="#dfn-iri"><abbr title="Internationalized Resource Identifier">IRI</abbr></a>.</p>

<p><a class="tref internalDFN" title="term" href="#dfn-term">Terms</a> or <a class="tref internalDFN" title="compact_iri" href="#dfn-compact_iri">compact IRIs</a> used as the value of a
  <code>@type</code> key may be defined within the same context. This means that one may specify a
  <a class="tref internalDFN" title="term" href="#dfn-term">term</a> like <code>xsd</code> and then use <code>xsd:integer</code> within the same
  context definition.</p>

<p>The example below demonstrates how a JSON-LD author can coerce values to
<a class="tref internalDFN" title="typed_value" href="#dfn-typed_value">typed values</a>, IRIs and lists.</p>

<div class="example"><div class="example-title"><span>Example 35</span>: Expanded term definition with types</div><pre class="example">{
  &quot;@context&quot;:
  {
    &quot;xsd&quot;: &quot;http://www.w3.org/2001/XMLSchema#&quot;,
    &quot;name&quot;: &quot;http://xmlns.com/foaf/0.1/name&quot;,
    &quot;age&quot;:
    <span class="diff">{
      &quot;@id&quot;: &quot;http://xmlns.com/foaf/0.1/age&quot;,
      &quot;@type&quot;: &quot;xsd:integer&quot;
    }</span>,
    &quot;homepage&quot;:
    <span class="diff">{
      &quot;@id&quot;: &quot;http://xmlns.com/foaf/0.1/homepage&quot;,
      &quot;@type&quot;: &quot;@id&quot;,
      &quot;@container&quot;: &quot;@list&quot;
    }</span>
  },
  &quot;@id&quot;: &quot;http://example.com/people#john&quot;,
  &quot;name&quot;: &quot;John Smith&quot;,
  &quot;age&quot;: <span class="diff">&quot;41&quot;</span>,
  &quot;homepage&quot;:
  <span class="diff">[
    &quot;http://personal.example.org/&quot;,
    &quot;http://work.example.com/jsmith/&quot;
  ]</span>
}</pre></div>

<p>The markup shown above would generate the following data. The data has no inherent order
  except for the values the <code>http://xmlns.com/foaf/0.1/homepage</code> property
  which represent an ordered list.</p>

<table class="example">
<thead>
  <tr><th>Subject</th>
  <th>Property</th>
  <th>Object</th>
  <th>Datatype</th>
</tr></thead>
<tbody>
<tr>
  <td>http://example.com/people#john</td>
  <td>http://xmlns.com/foaf/0.1/name</td>
  <td>John Smith</td>
  <td> </td>
</tr>
<tr>
  <td>http://example.com/people#john</td>
  <td>http://xmlns.com/foaf/0.1/age</td>
  <td>41</td>
  <td>http://www.w3.org/2001/XMLSchema#integer</td>
</tr>
<tr>
  <td rowspan="2">http://example.com/people#john</td>
  <td rowspan="2">http://xmlns.com/foaf/0.1/homepage</td>
  <td>http://personal.example.org/</td>
  <td> </td>
</tr>
<tr>
  <td>http://work.example.com/jsmith/</td>
  <td> </td>
</tr>
</tbody>
</table>

<p>Terms may also be defined using <a class="tref internalDFN" title="absolute_iri" href="#dfn-absolute_iri">absolute IRIs</a> or <a class="tref internalDFN" title="compact_iri" href="#dfn-compact_iri">compact IRIs</a>.
  This allows coercion rules to be applied to keys which are not represented as a simple <a class="tref internalDFN" title="term" href="#dfn-term">term</a>.
  For example:</p>

<div class="example"><div class="example-title"><span>Example 36</span>: Term definitions using compact and absolute IRIs</div><pre class="example">{
  &quot;@context&quot;:
  {
    &quot;foaf&quot;: &quot;http://xmlns.com/foaf/0.1/&quot;,
    &quot;<span class="diff">foaf:age</span>&quot;:
    {
      <span class="diff">&quot;@id&quot;: &quot;http://xmlns.com/foaf/0.1/age&quot;</span>,
      &quot;@type&quot;: &quot;xsd:integer&quot;
    },
    &quot;<span class="diff">http://xmlns.com/foaf/0.1/homepage</span>&quot;:
    {
      &quot;@type&quot;: &quot;@id&quot;
    }
  },
  &quot;foaf:name&quot;: &quot;John Smith&quot;,
  &quot;<span class="diff">foaf:age</span>&quot;: &quot;41&quot;,
  &quot;<span class="diff">http://xmlns.com/foaf/0.1/homepage</span>&quot;:
  [
    &quot;http://personal.example.org/&quot;,
    &quot;http://work.example.com/jsmith/&quot;
  ]
}</pre></div>

<p>In this case the <code>@id</code> definition in the term definition is optional, but if it does exist, the <a class="tref internalDFN" title="compact_iri" href="#dfn-compact_iri">compact <abbr title="Internationalized Resource Identifier">IRI</abbr></a>
  or <a class="tref internalDFN" title="iri" href="#dfn-iri"><abbr title="Internationalized Resource Identifier">IRI</abbr></a> is treated as a <a class="tref internalDFN" title="term" href="#dfn-term">term</a> (not a <code>prefix:suffix</code> construct)
  so that the actual definition of a <a class="tref internalDFN" title="prefix" href="#dfn-prefix">prefix</a> becomes unnecessary. Type coercion is performed using
  the unexpanded value of the key, which has to match exactly an entry in the <a class="tref internalDFN" title="active_context" href="#dfn-active_context">active context</a>.</p>

<div class="note"><div class="note-title"><span>Note</span></div><p class="">Keys in the context are treated as <a class="tref internalDFN" title="term" href="#dfn-term">terms</a> for the purpose of
  expansion and value coercion. At times, this may result in multiple representations for the same expanded <abbr title="Internationalized Resource Identifier">IRI</abbr>.
  For example, one could specify that <code>dog</code> and <code>cat</code> both expanded to <code>http://example.com/vocab#animal</code>.
  Doing this could be useful for establishing different type coercion or language specification rules. It also allows a <a class="tref internalDFN" title="compact_iri" href="#dfn-compact_iri">compact <abbr title="Internationalized Resource Identifier">IRI</abbr></a> (or even an
  absolute <a class="tref internalDFN" title="iri" href="#dfn-iri"><abbr title="Internationalized Resource Identifier">IRI</abbr></a>) to be defined as something else entirely. For example, one could specify that
  the <a class="tref internalDFN" title="term" href="#dfn-term">term</a> <code>http://example.org/zoo</code> should expand to
  <code>http://example.org/river</code>, but this usage is discouraged because it would lead to a
  great deal of confusion among developers attempting to understand the JSON-LD document.</p></div>


</section>


<section id="property-generators">
<h3><span class="secno">6.7 </span>Property Generators</h3>

<p>At times, an author may find that they need to express the same value for
multiple properties. The simplest approach to accomplish this goal would be
to do the following:</p>

<div class="example"><div class="example-title"><span>Example 37</span>: Verbose expression of multiple properties with the same value</div><pre class="example">{
  &quot;@context&quot;:
  {
    <span class="diff">&quot;title1&quot;: &quot;http://purl.org/dc/terms/title&quot;</span>,
    <span class="diff">&quot;title2&quot;: &quot;http://schema.org/name&quot;</span>,
    <span class="diff">&quot;title3&quot;: &quot;http://www.w3.org/2000/01/rdf-schema#label&quot;</span>
  },
  &quot;@id&quot;: &quot;http://example.com/book&quot;,
  <span class="diff">&quot;title1&quot;: &quot;The Count of Monte Cristo&quot;</span>,
  <span class="diff">&quot;title2&quot;: &quot;The Count of Monte Cristo&quot;</span>,
  <span class="diff">&quot;title3&quot;: &quot;The Count of Monte Cristo&quot;</span>
}</pre></div>

<p>Unfortunately, the approach above produces redundant data and would become a
publishing burden for large data sets.
In these situations, the author may use
a <dfn title="property_generator" id="dfn-property_generator">property generator</dfn> to express a <a class="tref internalDFN" title="term" href="#dfn-term">term</a> that maps to
multiple <a class="tref internalDFN" title="property" href="#dfn-property">properties</a> in the <a class="tref internalDFN" title="json-ld_graph" href="#dfn-json-ld_graph">JSON-LD graph</a>.
This method can be accomplished by using the following markup pattern:</p>

<div class="example"><div class="example-title"><span>Example 38</span>: Generating multiple properties using a single term</div><pre class="example">{
  &quot;@context&quot;:
  {
    <span class="diff">&quot;title&quot;: { &quot;@id&quot;: [ &quot;http://purl.org/dc/terms/title&quot;,
                        &quot;http://schema.org/name&quot;,
                        &quot;http://www.w3.org/2000/01/rdf-schema#label&quot; ] }</span>
  },
  &quot;@id&quot;: &quot;http://example.com/book&quot;,
  <span class="diff">&quot;title&quot;: &quot;The Count of Monte Cristo&quot;</span>
}</pre></div>

<p>While the term above is only used once outside of the <code>@context</code>,
the document above is equivalent to the following:</p>

<table class="example">
<thead>
  <tr><th>Subject</th>
  <th>Property</th>
  <th>Object</th>
</tr></thead>
<tbody>
<tr>
  <td>http://example.com/book</td>
  <td>http://purl.org/dc/terms/title</td>
  <td>The Count of Monte Cristo</td>
</tr>
<tr>
  <td>http://example.com/book</td>
  <td>http://schema.org/name</td>
  <td>The Count of Monte Cristo</td>
</tr>
<tr>
  <td>http://example.com/book</td>
  <td>http://www.w3.org/2000/01/rdf-schema#label</td>
  <td>The Count of Monte Cristo</td>
</tr>
</tbody>
</table>

</section>

<section id="iri-expansion-within-a-context">
  <h3><span class="secno">6.8 </span><abbr title="Internationalized Resource Identifier">IRI</abbr> Expansion Within a Context</h3>
  <p>In general, normal <abbr title="Internationalized Resource Identifier">IRI</abbr> expansion rules apply
    anywhere an <abbr title="Internationalized Resource Identifier">IRI</abbr> is expected (see <a href="#iris" class="sec-ref"><span class="secno">5.3</span> <span class="sec-title">IRIs</span></a>). Within
    a <a class="tref internalDFN" title="context" href="#dfn-context">context</a> definition, this can mean that terms defined
    within the context may also be used within that context as long as
    there are no circular dependencies. For example, it is common to use
    the <code>xsd</code> namespace when defining <a class="tref internalDFN" title="typed_value" href="#dfn-typed_value">typed value</a>s:</p>
<div class="example"><div class="example-title"><span>Example 39</span>: IRI expansion within a context</div><pre class="example">{
  &quot;@context&quot;:
  {
    <span class="diff">&quot;xsd&quot;: &quot;http://www.w3.org/2001/XMLSchema#&quot;</span>,
    &quot;name&quot;: &quot;http://xmlns.com/foaf/0.1/name&quot;,
    &quot;age&quot;:
    {
      &quot;@id&quot;: &quot;http://xmlns.com/foaf/0.1/age&quot;,
      &quot;@type&quot;: <span class="diff">&quot;xsd:integer&quot;</span>
    },
    &quot;homepage&quot;:
    {
      &quot;@id&quot;: &quot;http://xmlns.com/foaf/0.1/homepage&quot;,
      &quot;@type&quot;: &quot;@id&quot;
    }
  },
  ...
}</pre></div>
<p>In this example, the <code>xsd</code> <a class="tref internalDFN" title="term" href="#dfn-term">term</a> is defined
  and used as a <a class="tref internalDFN" title="prefix" href="#dfn-prefix">prefix</a> for the <code>@type</code> coercion
  of the <code>age</code> property.</p>

<p><a class="tref internalDFN" title="term" href="#dfn-term">Terms</a> may also be used when defining the <abbr title="Internationalized Resource Identifier">IRI</abbr> of another
<a class="tref internalDFN" title="term" href="#dfn-term">term</a>:</p>

<div class="example"><div class="example-title"><span>Example 40</span>: Using a term to define the IRI of another term within a context</div><pre class="example">{
  &quot;@context&quot;:
  {
    <span class="diff">&quot;foaf&quot;: &quot;http://xmlns.com/foaf/0.1/&quot;</span>,
    &quot;xsd&quot;: &quot;http://www.w3.org/2001/XMLSchema#&quot;,
    &quot;name&quot;: <span class="diff">&quot;foaf:name&quot;</span>,
    &quot;age&quot;:
    {
      &quot;@id&quot;: <span class="diff">&quot;foaf:age&quot;</span>,
      &quot;@type&quot;: &quot;xsd:integer&quot;
    },
    &quot;homepage&quot;:
    {
      &quot;@id&quot;: <span class="diff">&quot;foaf:homepage&quot;</span>,
      &quot;@type&quot;: &quot;@id&quot;
    }
  },
  ...
}</pre></div>

<p><a class="tref internalDFN" title="compact_iri" href="#dfn-compact_iri">Compact IRIs</a>
  and <a class="tref internalDFN" title="iri" href="#dfn-iri">IRIs</a> may be used on the left-hand side of a
  <a class="tref internalDFN" title="term" href="#dfn-term">term</a> definition.</p>

<div class="example"><div class="example-title"><span>Example 41</span>: Using a compact IRI as a term</div><pre class="example">{
  &quot;@context&quot;:
  {
    <span class="diff">&quot;foaf&quot;: &quot;http://xmlns.com/foaf/0.1/&quot;</span>,
    &quot;xsd&quot;: &quot;http://www.w3.org/2001/XMLSchema#&quot;,
    &quot;name&quot;: &quot;foaf:name&quot;,
    &quot;<span class="diff">foaf:age</span>&quot;:
    {
      &quot;@type&quot;: &quot;xsd:integer&quot;
    },
    &quot;<span class="diff">foaf:homepage</span>&quot;:
    <span class="diff">{
      &quot;@type&quot;: &quot;@id&quot;
    }</span>
  },
  ...
}</pre></div>

<p>
In this example, the <a class="tref internalDFN" title="compact_iri" href="#dfn-compact_iri">compact <abbr title="Internationalized Resource Identifier">IRI</abbr></a> form is used in two different
ways.
In the first approach, <code>foaf:age</code> declares both the
<a class="tref internalDFN" title="iri" href="#dfn-iri"><abbr title="Internationalized Resource Identifier">IRI</abbr></a> for the <a class="tref internalDFN" title="term" href="#dfn-term">term</a> (using short-form) as well as the
<code>@type</code> associated with the <a class="tref internalDFN" title="term" href="#dfn-term">term</a>. In the second
approach, only the <code>@type</code> associated with the <a class="tref internalDFN" title="term" href="#dfn-term">term</a> is
specified. The full <a class="tref internalDFN" title="iri" href="#dfn-iri"><abbr title="Internationalized Resource Identifier">IRI</abbr></a> for
<code>foaf:homepage</code> is determined by looking up the <code>foaf</code>
<a class="tref internalDFN" title="prefix" href="#dfn-prefix">prefix</a> in the
<a class="tref internalDFN" title="context" href="#dfn-context">context</a>.
</p>

<p>
<a class="tref internalDFN" title="absolute_iri" href="#dfn-absolute_iri">Absolute IRIs</a> may also be used in the key position in a <a class="tref internalDFN" title="context" href="#dfn-context">context</a>:
</p>

<div class="example"><div class="example-title"><span>Example 42</span>: Associating context definitions with absolute IRIs</div><pre class="example">{
  &quot;@context&quot;:
  {
    &quot;foaf&quot;: &quot;http://xmlns.com/foaf/0.1/&quot;,
    &quot;xsd&quot;: &quot;http://www.w3.org/2001/XMLSchema#&quot;,
    &quot;name&quot;: &quot;foaf:name&quot;,
    &quot;foaf:age&quot;:
    {
      &quot;@id&quot;: &quot;foaf:age&quot;,
      &quot;@type&quot;: &quot;xsd:integer&quot;
    },
    &quot;<span class="diff">http://xmlns.com/foaf/0.1/homepage</span>&quot;:
    {
      &quot;@type&quot;: &quot;@id&quot;
    }
  },
  ...
}</pre></div>

<p>
In order for the <a class="tref internalDFN" title="absolute_iri" href="#dfn-absolute_iri">absolute <abbr title="Internationalized Resource Identifier">IRI</abbr></a> to match above, the <a class="tref internalDFN" title="absolute_iri" href="#dfn-absolute_iri">absolute <abbr title="Internationalized Resource Identifier">IRI</abbr></a> needs to be used in the <a class="tref internalDFN" title="json-ld_document" href="#dfn-json-ld_document">JSON-LD document</a>. Also note that <code>foaf:homepage</code>
will not use the <code>{ &quot;@type&quot;: &quot;@id&quot; }</code> declaration because
<code>foaf:homepage</code> is not the same as
<code>http://xmlns.com/foaf/0.1/homepage</code>. That is, <a class="tref internalDFN" title="term" href="#dfn-term">terms</a>
are looked up in a <a class="tref internalDFN" title="context" href="#dfn-context">context</a> using direct string comparison before the
<a class="tref internalDFN" title="prefix" href="#dfn-prefix">prefix</a> lookup mechanism is applied.
</p>

<p>The only exception for using terms in the <a class="tref internalDFN" title="context" href="#dfn-context">context</a> is that
  circular definitions are not allowed. That is,
  a definition of <em>term-1</em> cannot depend on the
  definition of <em>term-2</em> if <em>term-2</em> also depends on
  <em>term-1</em>. For example, the following <a class="tref internalDFN" title="context" href="#dfn-context">context</a> definition
  is illegal:</p>
<div class="example"><div class="example-title"><span>Example 43</span>: Illegal circular definition of terms within a context</div><pre class="example">{
  &quot;@context&quot;:
  {
    <span class="diff">&quot;term1&quot;: &quot;term2:foo&quot;,
    &quot;term2&quot;: &quot;term1:bar&quot;</span>
  },
  ...
}</pre></div>
</section>

<section id="sets-and-lists">
<h3><span class="secno">6.9 </span>Sets and Lists</h3>

<p>A JSON-LD author can express multiple values in a compact way by using
  <a class="tref internalDFN" title="array" href="#dfn-array">arrays</a>. Since graphs do not describe ordering for links
  between nodes, arrays in JSON-LD do not provide an ordering of the
  contained elements by default. This is exactly the opposite from regular JSON
  arrays, which are ordered by default. For example, consider the following
  simple document:</p>

<div class="example"><div class="example-title"><span>Example 44</span>: Multiple values with no inherent order</div><pre class="example">{
...
  &quot;@id&quot;: &quot;http://example.org/people#joebob&quot;,
  &quot;nick&quot;: <span class="diff">[ &quot;joe&quot;, &quot;bob&quot;, &quot;jaybee&quot; ]</span>,
...
}</pre></div>

<p>The markup shown above would result in the following data being generated,
  each relating the node to an individual value, with no inherent order:</p>

<table class="example">
<thead>
  <tr><th>Subject</th>
  <th>Property</th>
  <th>Object</th>
</tr></thead>
<tbody>
<tr>
  <td>http://example.org/people#joebob</td>
  <td>http://xmlns.com/foaf/0.1/nick</td>
  <td>joe</td>
</tr>
<tr>
  <td>http://example.org/people#joebob</td>
  <td>http://xmlns.com/foaf/0.1/nick</td>
  <td>bob</td>
</tr>
<tr>
  <td>http://example.org/people#joebob</td>
  <td>http://xmlns.com/foaf/0.1/nick</td>
  <td>jaybee</td>
</tr>
</tbody>
</table>

<p>Multiple values may also be expressed using the expanded form:</p>

<div class="example"><div class="example-title"><span>Example 45</span>: Using an expanded form to set multiple values</div><pre class="example">{
  &quot;@id&quot;: &quot;http://example.org/articles/8&quot;,
  &quot;dc:title&quot;: <span class="diff">
  [
    {
      &quot;@value&quot;: &quot;Das Kapital&quot;,
      &quot;@language&quot;: &quot;de&quot;
    },
    {
      &quot;@value&quot;: &quot;Capital&quot;,
      &quot;@language&quot;: &quot;en&quot;
    }
  ]</span>
}</pre></div>

<p>The markup shown above would generate the following data, again with
  no inherent order:</p>

<table class="example">
<thead>
  <tr><th>Subject</th>
  <th>Property</th>
  <th>Object</th>
  <th>Language</th>
</tr></thead>
<tbody>
<tr>
  <td>http://example.org/articles/8</td>
  <td>http://purl.org/dc/terms/title</td>
  <td>Das Kapital</td>
  <td>de</td>
</tr>
<tr>
  <td>http://example.org/articles/8</td>
  <td>http://purl.org/dc/terms/title</td>
  <td>Capital</td>
  <td>en</td>
</tr>
</tbody>
</table>

<p>As the notion of ordered collections is rather important in data
  modeling, it is useful to have specific language support. In JSON-LD,
  a list may be represented using the <code>@list</code> <a class="tref internalDFN" title="keyword" href="#dfn-keyword">keyword</a> as follows:</p>
<div class="example"><div class="example-title"><span>Example 46</span>: An ordered collection of values in JSON-LD</div><pre class="example">{
...
  &quot;@id&quot;: &quot;http://example.org/people#joebob&quot;,
  &quot;foaf:nick&quot;:
  <span class="diff">{
    &quot;@list&quot;: [ &quot;joe&quot;, &quot;bob&quot;, &quot;jaybee&quot; ]
  }</span>,
...
}</pre></div>

<p>This describes the use of this <a class="tref internalDFN" title="array" href="#dfn-array">array</a> as being ordered,
  and order is maintained when processing a document. If every use of a given multi-valued
  property is a list, this may be abbreviated by setting <code>@container</code>
  to <code>@list</code> in the <a class="tref internalDFN" title="context" href="#dfn-context">context</a>:</p>
<div class="example"><div class="example-title"><span>Example 47</span>: Specifying that a collection is ordered in the context</div><pre class="example">{
  <span class="diff">&quot;@context&quot;:
  {
    ...
    &quot;nick&quot;:
    {
      &quot;@id&quot;: &quot;http://xmlns.com/foaf/0.1/nick&quot;,
      &quot;@container&quot;: &quot;@list&quot;
    }
  }</span>,
...
  &quot;@id&quot;: &quot;http://example.org/people#joebob&quot;,
  &quot;nick&quot;: <span class="diff">[ &quot;joe&quot;, &quot;bob&quot;, &quot;jaybee&quot; ]</span>,
...
}</pre></div>

<div class="note"><div class="note-title"><span>Note</span></div><p class="">List of lists are not allowed in this version of JSON-LD.
  This decision was made due to the extreme amount of added complexity when
  processing lists of lists.</p></div>

<p>Similarly to <code>@list</code>, there exists the <a class="tref internalDFN" title="keyword" href="#dfn-keyword">keyword</a> <code>@set</code> to
  describe unordered sets. While its use in the body of a JSON-LD document
  represents just syntactic sugar optimized away when processing
  the document, it is very helpful when used within the context of a document.
  Values of terms associated with a <code>@set</code> or <code>@list</code> container
  are always represented in the form of an <a class="tref internalDFN" title="array" href="#dfn-array">array</a> - even if there is just a
  single value that would otherwise be optimized to a non-array form in a
  <a href="#compact-document-form" class="sec-ref"><span class="secno">6.17</span> <span class="sec-title">Compact Document Form</span></a>. This makes post-processing of
  the data easier as the data is always in array form, even if the array only
  contains a single value.</p>

<div class="note"><div class="note-title"><span>Note</span></div><p class="">The use of <code>@container</code> in the body of a JSON-LD
  document has no meaning and is not allowed by the JSON-LD grammar (see <a href="#json-ld-grammar" class="sec-ref"><span class="secno">B.</span> <span class="sec-title">JSON-LD Grammar</span></a>).</p></div>

</section>

<section id="embedding">
  <h3><span class="secno">6.10 </span>Embedding</h3>

  <p><dfn title="embedding" id="dfn-embedding">Embedding</dfn> is a JSON-LD feature that allows an author to
    use <a class="tref internalDFN" title="node_object" href="#dfn-node_object">node objects</a> as
    <a class="tref internalDFN" title="property" href="#dfn-property">property</a> values. This is a commonly used mechanism for
    creating a parent-child relationship between two <a class="tref internalDFN" title="node" href="#dfn-node">nodes</a>.</p>

  <p>The example shows two nodes related by a property from the first node:</p>

  <div class="example"><div class="example-title"><span>Example 48</span>: Embedding a node object as property value of another node object</div><pre class="example">{
...
  &quot;name&quot;: &quot;Manu Sporny&quot;,
  &quot;<span class="diff">knows</span>&quot;:
  {
    &quot;<span class="diff">@type</span>&quot;: &quot;<span class="diff">Person</span>&quot;,
    &quot;<span class="diff">name</span>&quot;: &quot;<span class="diff">Gregg Kellogg</span>&quot;,
  }
...
}</pre></div>

  <p>
    A <a class="tref internalDFN" title="node_object" href="#dfn-node_object">node object</a>, like the one used above, may be used in
    any value position in the body of a JSON-LD document.</p>
</section>

<section id="named-graphs">
  <h3><span class="secno">6.11 </span>Named Graphs</h3>

  <p>At times, it is necessary to make statements about a <a class="tref internalDFN" title="json-ld_graph" href="#dfn-json-ld_graph">JSON-LD graph</a>
    itself, rather than just a single <a class="tref internalDFN" title="node" href="#dfn-node">node</a>. This can be done by
    grouping a set of <a class="tref internalDFN" title="node" href="#dfn-node">nodes</a> using the <code>@graph</code>
    <a class="tref internalDFN" title="keyword" href="#dfn-keyword">keyword</a>. A developer may also name data expressed using the
    <code>@graph</code> <a class="tref internalDFN" title="keyword" href="#dfn-keyword">keyword</a> by pairing it with an
    <code>@id</code> <a class="tref internalDFN" title="keyword" href="#dfn-keyword">keyword</a> as shown in the following example:</p>

  <div class="example"><div class="example-title"><span>Example 49</span>: Identifying and making statements about a graph</div><pre class="example">{
  &quot;@context&quot;: {
    &quot;generatedAt&quot;: &quot;http://www.w3.org/ns/prov#generatedAtTime&quot;,
    &quot;Person&quot;: &quot;http://xmlns.com/foaf/0.1/Person&quot;,
    &quot;name&quot;: &quot;http://xmlns.com/foaf/0.1/name&quot;,
    &quot;knows&quot;: &quot;http://xmlns.com/foaf/0.1/knows&quot;,
    &quot;xsd&quot;: &quot;http://www.w3.org/2001/XMLSchema#&quot;
  },
  <span class="diff">&quot;@id&quot;: &quot;http://example.org/graphs/73&quot;,
  &quot;generatedAt&quot;: { &quot;@value&quot;: &quot;2012-04-09&quot;, &quot;@type&quot;: &quot;xsd:date&quot; },
  &quot;@graph&quot;:</span>
  [
    {
      &quot;@id&quot;: &quot;http://manu.sporny.org/i/public&quot;,
      &quot;@type&quot;: &quot;Person&quot;,
      &quot;name&quot;: &quot;Manu Sporny&quot;,
      &quot;knows&quot;: &quot;http://greggkellogg.net/foaf#me&quot;
    },
    {
      &quot;@id&quot;: &quot;http://greggkellogg.net/foaf#me&quot;,
      &quot;@type&quot;: &quot;Person&quot;,
      &quot;name&quot;: &quot;Gregg Kellogg&quot;,
      &quot;knows&quot;: &quot;http://manu.sporny.org/i/public&quot;
    }
  ]
}</pre></div>

  <p>The example above expresses a <em>named</em> <a class="tref internalDFN" title="json-ld_graph" href="#dfn-json-ld_graph">JSON-LD graph</a>
    that is identified by the <a class="tref internalDFN" title="iri" href="#dfn-iri"><abbr title="Internationalized Resource Identifier">IRI</abbr></a>
    <code>http://example.org/graphs/73</code>. That graph is composed of the
    statements about Manu and Gregg. Metadata about the graph itself is also
    expressed via the <code>generatedAt</code> property, which specifies when
    the graph was generated. An alternative view of the
    information above is represented in table form below:</p>

  <table class="example">
  <thead>
    <tr><th>Graph</th>
    <th>Subject</th>
    <th>Property</th>
    <th>Object</th>
    <th>Datatype</th>
  </tr></thead>
  <tbody>
  <tr>
    <td>http://example.org/graphs/73</td>
    <td>http://example.org/graphs/73</td>
    <td>http://www.w3.org/ns/prov#generatedAtTime</td>
    <td>2012-04-09</td>
    <td>http://www.w3.org/2001/XMLSchema#date</td>
  </tr>
  <tr>
    <td>http://example.org/graphs/73</td>
    <td>http://manu.sporny.org/i/public</td>
    <td>http://www.w3.org/2001/XMLSchema#type</td>
    <td>http://xmlns.com/foaf/0.1/Person</td>
    <td></td>
  </tr>
  <tr>
    <td>http://example.org/graphs/73</td>
    <td>http://manu.sporny.org/i/public</td>
    <td>http://xmlns.com/foaf/0.1/name</td>
    <td>Manu Sporny</td>
    <td></td>
  </tr>
  <tr>
    <td>http://example.org/graphs/73</td>
    <td>http://manu.sporny.org/i/public</td>
    <td>http://xmlns.com/foaf/0.1/knows</td>
    <td>http://greggkellogg.net/foaf#me</td>
    <td></td>
  </tr>
  <tr>
    <td>http://example.org/graphs/73</td>
    <td>http://greggkellogg.net/foaf#me</td>
    <td>http://www.w3.org/2001/XMLSchema#type</td>
    <td>http://xmlns.com/foaf/0.1/Person</td>
    <td></td>
  </tr>
  <tr>
    <td>http://example.org/graphs/73</td>
    <td>http://greggkellogg.net/foaf#me</td>
    <td>http://xmlns.com/foaf/0.1/name</td>
    <td>Gregg Kellogg</td>
    <td></td>
  </tr>
  <tr>
    <td>http://example.org/graphs/73</td>
    <td>http://greggkellogg.net/foaf#me</td>
    <td>http://xmlns.com/foaf/0.1/knows</td>
    <td>http://manu.sporny.org/i/public</td>
    <td></td>
  </tr>
  </tbody>
  </table>

  <p>When <code>@graph</code> is used in a document's top-level object which
    has no other <a class="tref internalDFN" title="property" href="#dfn-property">properties</a> that are mapped
    to an <a class="tref internalDFN" title="iri" href="#dfn-iri"><abbr title="Internationalized Resource Identifier">IRI</abbr></a> or a <a class="tref internalDFN" title="keyword" href="#dfn-keyword">keyword</a> it is considered to
    express the otherwise implicit default graph. This mechanism can be useful
    when a number of <a class="tref internalDFN" title="node" href="#dfn-node">nodes</a> thay may not directly
    relate to one another through a property or where <a class="tref internalDFN" title="embedding" href="#dfn-embedding">embedding</a>
    is not desirable to the application. For example:</p>

  <div class="example"><div class="example-title"><span>Example 50</span>: Using @graph to explicitly express the default graph</div><pre class="example">{
  &quot;@context&quot;: ...,
  &quot;<span class="diff">@graph</span>&quot;:
  [
    {
      &quot;@id&quot;: &quot;http://manu.sporny.org/i/public&quot;,
      &quot;@type&quot;: &quot;foaf:Person&quot;,
      &quot;name&quot;: &quot;Manu Sporny&quot;,
      &quot;knows&quot;: &quot;http://greggkellogg.net/foaf#me&quot;
    },
    {
      &quot;@id&quot;: &quot;http://greggkellogg.net/foaf#me&quot;,
      &quot;@type&quot;: &quot;foaf:Person&quot;,
      &quot;name&quot;: &quot;Gregg Kellogg&quot;,
      &quot;knows&quot;: &quot;http://manu.sporny.org/i/public&quot;
    }
  ]
}</pre></div>

  <p>In this case, embedding doesn't work as each <a class="tref internalDFN" title="node_object" href="#dfn-node_object">node object</a>
    references the other. Using the <code>@graph</code> <a class="tref internalDFN" title="keyword" href="#dfn-keyword">keyword</a>
    allows multiple <a class="tref internalDFN" title="node" href="#dfn-node">nodes</a> to be defined within an
    <a class="tref internalDFN" title="array" href="#dfn-array">array</a>, and allows the use of a shared <a class="tref internalDFN" title="context" href="#dfn-context">context</a>.
    This is equivalent to using multiple
    <a class="tref internalDFN" title="node_object" href="#dfn-node_object">node objects</a> in array and defining
    the <code>@context</code> within each <a class="tref internalDFN" title="node_object" href="#dfn-node_object">node object</a>:</p>

  <div class="example"><div class="example-title"><span>Example 51</span>: Context needs to be duplicated if @graph is not used</div><pre class="example">[
  {
    <span class="diff">&quot;@context&quot;: ...,</span>
    &quot;@id&quot;: &quot;http://manu.sporny.org/i/public&quot;,
    &quot;@type&quot;: &quot;foaf:Person&quot;,
    &quot;name&quot;: &quot;Manu Sporny&quot;,
    &quot;knows&quot;: &quot;http://greggkellogg.net/foaf#me&quot;
  },
  {
    <span class="diff">&quot;@context&quot;: ...,</span>
    &quot;@id&quot;: &quot;http://greggkellogg.net/foaf#me&quot;,
    &quot;@type&quot;: &quot;foaf:Person&quot;,
    &quot;name&quot;: &quot;Gregg Kellogg&quot;,
    &quot;knows&quot;: &quot;http://manu.sporny.org/i/public&quot;
  }
]</pre></div>

</section>

<section id="identifying-blank-nodes">
  <h3><span class="secno">6.12 </span>Identifying Blank Nodes</h3>

  <p>At times, it becomes necessary to be able to express information without
    being able to specify the node. This type of node is called a <a class="tref internalDFN" title="blank_node" href="#dfn-blank_node">blank node</a>
    (see <cite><a href="http://www.w3.org/TR/rdf11-concepts/#section-blank-nodes">Section 3.4: Blank Nodes</a></cite>
    of [<cite><a class="bibref" href="#bib-RDF-CONCEPTS">RDF-CONCEPTS</a></cite>]). In JSON-LD, <a class="tref internalDFN" title="blank_node_identifier" href="#dfn-blank_node_identifier">blank node identifiers</a> are
    automatically created if a node is not specified using the <code>@id</code> <a class="tref internalDFN" title="keyword" href="#dfn-keyword">keyword</a>.
    However, authors may provide identifiers for <a class="tref internalDFN" title="blank_node" href="#dfn-blank_node">blank nodes</a>
    by using the special <code>_</code> (underscore) <a class="tref internalDFN" title="prefix" href="#dfn-prefix">prefix</a>. This allows one
    to reference the node locally within the document, but makes it impossible to reference
    the node from an external document. The <a class="tref internalDFN" title="blank_node_identifier" href="#dfn-blank_node_identifier">blank node identifier</a> is scoped
    to the document in which it is used.</p>

  <div class="example"><div class="example-title"><span>Example 52</span>: Specifying a local blank node identifier</div><pre class="example">{
...
  &quot;@id&quot;: &quot;<span class="diff">_:foo</span>&quot;,
...
}</pre></div>

  <p>The example above would set the node to <code>_:foo</code>, which can
    then be used elsewhere in the JSON-LD document to refer back to the
    <a class="tref internalDFN" title="blank_node" href="#dfn-blank_node">blank node</a>. If a developer finds that they refer to the <a class="tref internalDFN" title="blank_node" href="#dfn-blank_node">blank node</a>
    more than once, they should consider naming the node using a dereferenceable
    <a class="tref internalDFN" title="iri" href="#dfn-iri"><abbr title="Internationalized Resource Identifier">IRI</abbr></a> so that it can also be referenced from other documents.</p>
</section>

<section id="aliasing-keywords">
<h3><span class="secno">6.13 </span>Aliasing Keywords</h3>

<p>Each of the JSON-LD <a class="tref internalDFN" title="keyword" href="#dfn-keyword">keywords</a>,
except for <code>@context</code>, may be aliased to application-specific
keywords. This feature allows legacy JSON content to be utilized
by JSON-LD by re-using JSON keys that already exist in legacy documents.
This feature also allows developers to design domain-specific implementations
using only the JSON-LD <a class="tref internalDFN" title="context" href="#dfn-context">context</a>.</p>

<div class="example"><div class="example-title"><span>Example 53</span>: Aliasing keywords</div><pre class="example">{
  &quot;@context&quot;:
  {
     <span class="diff">&quot;url&quot;: &quot;@id&quot;</span>,
     <span class="diff">&quot;a&quot;: &quot;@type&quot;</span>,
     &quot;name&quot;: &quot;http://schema.org/name&quot;
  },
  &quot;<span class="diff">url</span>&quot;: &quot;http://example.com/about#gregg&quot;,
  &quot;<span class="diff">a</span>&quot;: &quot;http://schema.org/Person&quot;,
  &quot;name&quot;: &quot;Gregg Kellogg&quot;
}</pre></div>

<p>In the example above, the <code>@id</code> and <code>@type</code>
<a class="tref internalDFN" title="keyword" href="#dfn-keyword">keywords</a> have been given the aliases <strong>url</strong> and
<strong>a</strong>, respectively.
</p>

</section>

<section id="data-annotations">
<h3><span class="secno">6.14 </span>Data Annotations</h3>

<p>It is common for developers using JSON to organize their data in ways
that makes working with the data more efficient. It is often that these methods 
of organizing data are not meant to express Linked Data, but should survive
transformation by JSON-LD. For example, if a developer 
organizes employees in a JSON-LD document by a company-issued ID number, 
JSON-LD should not destroy that 'database index' when transforming the data. 
Data annotations allow content that would otherwise be removed from 
a JSON-LD graph to be
preserved by instructing the JSON-LD processor to syntactically preserve 
the annotation information and continue processing deeper into the JSON 
data structure.</p>

<div class="example"><div class="example-title"><span>Example 54</span>: Data annotations</div><pre class="example">{
  &quot;@context&quot;:
  {
     &quot;schema&quot;: &quot;http://schema.org/&quot;,
     &quot;Article&quot;: &quot;schema:Blog&quot;,
     &quot;name&quot;: &quot;schema:name&quot;,
     &quot;articleBody&quot;: &quot;schema:articleBody&quot;,
     &quot;wordCount&quot;: &quot;schema:wordCount&quot;,
     &quot;commentCount&quot;: &quot;http://example.com/schema/wordCount&quot;,
     &quot;blogPost&quot;: {
       &quot;@id&quot;: &quot;schema:blogPost&quot;,
       <span class="diff">&quot;@container&quot;: &quot;@annotation&quot;</span>
  },
  &quot;@id&quot;: &quot;http://example.com/&quot;,
  &quot;@type&quot;: &quot;Blog&quot;,
  &quot;name&quot;: &quot;World Financial News&quot;,
  <span class="diff">&quot;blogPost&quot;: {
     &quot;en&quot;: {
       &quot;@id&quot;: &quot;http://example.com/posts/1/en&quot;,
       &quot;articleBody&quot;: &quot;World commodities were up today with heavy trading of crude oil...&quot;,
       &quot;wordCount&quot;: 1539,
       &quot;commentCount&quot;: 64
     },
     &quot;de&quot;: {
       &quot;@id&quot;: &quot;http://example.com/posts/1/de&quot;,
       &quot;articleBody&quot;: &quot;Welt Rohstoffe waren bis heute mit schweren Handel mit Rohöl...&quot;,
       &quot;wordCount&quot;: 1204,
       &quot;commentCount&quot;: 23
     }</span>
  }
}</pre></div>

<p>In the example above, the <strong>blogPost</strong> <a class="tref internalDFN" title="term" href="#dfn-term">term</a> has
been marked as a <em>data annotation container</em>. The <strong>en</strong>,
<strong>de</strong>, and <strong>ja</strong> keys will effectively be ignored
semantically, but preserved syntactically, by the JSON-LD Processor as 
<em>annotations</em>. The interpretation of the data above is expressed in 
the table below. Note how the annotations do not appear in the Linked Data
below, but would continue to exist if the document were compacted or expanded 
using a JSON-LD processor:
</p>

  <table class="example">
  <thead>
    <tr><th>Subject</th>
    <th>Property</th>
    <th>Object</th>
    <th>Datatype</th>
  </tr></thead>
  <tbody>
  <tr>
    <td>http://example.com/</td>
    <td>http://www.w3.org/1999/02/22-rdf-syntax-ns#type</td>
    <td>http://schema.org/Blog</td>
    <td></td>
  </tr>
  <tr>
    <td>http://example.com/</td>
    <td>http://schema.org/name</td>
    <td>World Financial News</td>
    <td></td>
  </tr>
  <tr>
    <td>http://example.com/</td>
    <td>http://schema.org/blogPost</td>
    <td>http://example.com/posts/1/en</td>
    <td></td>
  </tr>
  <tr>
    <td>http://example.com/</td>
    <td>http://schema.org/blogPost</td>
    <td>http://example.com/posts/1/de</td>
    <td></td>
  </tr>
  <tr>
    <td>http://example.com/posts/1/en</td>
    <td>http://schema.org/articleBody</td>
    <td>World commodities were up today with heavy trading of crude oil...</td>
    <td></td>
  </tr>
  <tr>
    <td>http://example.com/posts/1/en</td>
    <td>http://schema.org/wordCount</td>
    <td>1539</td>
    <td>http://www.w3.org/2001/XMLSchema#integer</td>
  </tr>
  <tr>
    <td>http://example.com/posts/1/en</td>
    <td>http://example.com/schema/commentCount</td>
    <td>64</td>
    <td>http://www.w3.org/2001/XMLSchema#integer</td>
  </tr>
  <tr>
    <td>http://example.com/posts/1/de</td>
    <td>http://schema.org/articleBody</td>
    <td>Welt Rohstoffe waren bis heute mit schweren Handel mit Rohöl...</td>
    <td></td>
  </tr>
  <tr>
    <td>http://example.com/posts/1/de</td>
    <td>http://schema.org/wordCount</td>
    <td>1204</td>
    <td>http://www.w3.org/2001/XMLSchema#integer</td>
  </tr>
  <tr>
    <td>http://example.com/posts/1/de</td>
    <td>http://example.com/schema/commentCount</td>
    <td>23</td>
    <td>http://www.w3.org/2001/XMLSchema#integer</td>
  </tr>
  </tbody>
  </table>

</section>

<section id="explicitly-ignoring-data">
<h3><span class="secno">6.15 </span>Explicitly Ignoring Data</h3>

<p>At times, it becomes necessary to explicitly ignore data expressed in JSON
documents because it has no semantic meaning. For example, when the
<code>@vocab</code> keyword is used, every key in a JSON-LD object is 
appended to the vocabulary <a class="tref internalDFN" title="iri" href="#dfn-iri"><abbr title="Internationalized Resource Identifier">IRI</abbr></a>. The author may not want that
behavior to apply to every key, and it may be easier to specify just the keys
that they want the JSON-LD processor to ignore. For this purpose, an author
may associate the <a class="tref internalDFN" title="null" href="#dfn-null">null</a> keyword with a <a class="tref internalDFN" title="term" href="#dfn-term">term</a> in the
JSON-LD Context.</p>

<div class="example"><div class="example-title"><span>Example 55</span>: Using the null keyword to ignore data</div><pre class="example">{
  &quot;@context&quot;:
  {
     &quot;@vocab&quot;: &quot;http://schema.org/&quot;,
     <span class="diff">&quot;databaseId&quot;: null</span>
  },
  &quot;name&quot;: &quot;Manu Sporny&quot;,
  &quot;description&quot;: &quot;That guy&quot;,
  &quot;gender&quot;: &quot;Male&quot;,
  <span class="diff">&quot;databaseId&quot;: &quot;23987520&quot;</span>
}</pre></div>

<p>In the example above, the author has used <code>@vocab</code> as the base
<abbr title="Internationalized Resource Identifier">IRI</abbr> for all terms in the document, but has expressed that the
<code>databaseId</code> value should not be processed by the JSON-LD processor
by associating it with the <a class="tref internalDFN" title="null" href="#dfn-null">null</a> keyword in the JSON-LD Context.
</p>

</section>

<section id="expanded-document-form">
<h3><span class="secno">6.16 </span>Expanded Document Form</h3>
<p>The JSON-LD API [<cite><a class="bibref" href="#bib-JSON-LD-API">JSON-LD-API</a></cite>] defines an method for <em>expanding</em> a
  JSON-LD document.
  Expansion is the process of taking a JSON-LD document and applying a
  <code>@context</code> such that all IRIs, types, and values
  are expanded so that the <code>@context</code> is no longer necessary.</p>

<p>For example, assume the following JSON-LD input document:</p>

<div class="example"><div class="example-title"><span>Example 56</span>: Sample JSON-LD document</div><pre class="example">{
   &quot;@context&quot;:
   {
      &quot;name&quot;: &quot;http://xmlns.com/foaf/0.1/name&quot;,
      &quot;homepage&quot;: {
        &quot;@id&quot;: &quot;http://xmlns.com/foaf/0.1/homepage&quot;,
        &quot;@type&quot;: &quot;@id&quot;
      }
   },
   &quot;name&quot;: &quot;Manu Sporny&quot;,
   &quot;homepage&quot;: &quot;http://manu.sporny.org/&quot;
}</pre></div>

<p>Running the JSON-LD Expansion algorithm against the JSON-LD input document
  provided above would result in the following output:</p>

<div class="example"><div class="example-title"><span>Example 57</span>: Expanded form for the previous example</div><pre class="example">[
  {
    &quot;http://xmlns.com/foaf/0.1/name&quot;: [
      { &quot;@value&quot;: &quot;Manu Sporny&quot; }
    ],
    &quot;http://xmlns.com/foaf/0.1/homepage&quot;: [
      { &quot;@id&quot;: &quot;http://manu.sporny.org/&quot; }
    ]
  }
]</pre></div>

<p>Expanded document form is useful when an application has to process input
data in a deterministic form. It has been optimized to ensure that the code
that developers have to write is minimized compared to the code that would
have to be written to operate on
<a href="#compact-document-form" class="sec-ref"><span class="secno">6.17</span> <span class="sec-title">Compact Document Form</span></a>.</p>

</section>

<section id="compact-document-form">
<h3><span class="secno">6.17 </span>Compact Document Form</h3>
<p>The JSON-LD API [<cite><a class="bibref" href="#bib-JSON-LD-API">JSON-LD-API</a></cite>] defines a method for <em>compacting</em> a JSON-LD document.
  Compaction is the process of taking a JSON-LD document and applying a
  context such that the most compact form of the document is generated. JSON
  is typically expressed in a very compact, key-value format. That is, full
  IRIs are rarely used as keys. At times, a JSON-LD document may be received
  that is not in its most compact form. JSON-LD, via the API, provides a way
  to compact a JSON-LD document.</p>

<p>For example, assume the following JSON-LD input document:</p>

<div class="example"><div class="example-title"><span>Example 58</span>: Sample expanded JSON-LD document</div><pre class="example">[
  {
    &quot;http://xmlns.com/foaf/0.1/name&quot;: [ &quot;Manu Sporny&quot; ],
    &quot;http://xmlns.com/foaf/0.1/homepage&quot;: [
      {
       &quot;@id&quot;: &quot;http://manu.sporny.org/&quot;
      }
    ]
  }
]</pre></div>

<p>Additionally, assume the following developer-supplied JSON-LD context:</p>

<div class="example"><div class="example-title"><span>Example 59</span>: Sample context</div><pre class="example">{
  &quot;@context&quot;: {
    &quot;name&quot;: &quot;http://xmlns.com/foaf/0.1/name&quot;,
    &quot;homepage&quot;: {
      &quot;@id&quot;: &quot;http://xmlns.com/foaf/0.1/homepage&quot;,
      &quot;@type&quot;: &quot;@id&quot;
    }
  }
}</pre></div>

<p>Running the JSON-LD Compaction algorithm given the context supplied above
  against the JSON-LD input document provided above would result in the following
  output:</p>

<div class="example"><div class="example-title"><span>Example 60</span>: Compact form of the sample document once sample context has been applied</div><pre class="example">{
  &quot;@context&quot;: {
    &quot;name&quot;: &quot;http://xmlns.com/foaf/0.1/name&quot;,
    &quot;homepage&quot;: {
      &quot;@id&quot;: &quot;http://xmlns.com/foaf/0.1/homepage&quot;,
      &quot;@type&quot;: &quot;@id&quot;
    }
  },
  &quot;name&quot;: &quot;Manu Sporny&quot;,
  &quot;homepage&quot;: &quot;http://manu.sporny.org/&quot;
}</pre></div>

<p>The compaction algorithm enables a developer to map any document into an
  application-specific compacted form by first <a href="#expanded-document-form" class="sec-ref"><span class="secno">6.16</span> <span class="sec-title">Expanded Document Form</span></a>.
  While the context provided above mapped <code>http://xmlns.com/foaf/0.1/name</code>
  to <strong>name</strong>, it could have also mapped it to any arbitrary string
  provided by the developer. This powerful mechanism allows the developer to
  re-shape the incoming JSON data into a format that is optimized for
  their application.</p>
</section>

</section>

<section class="appendix normative" id="data-model">
  
<!--OddPage-->
<h2><span class="secno">A. </span>Data Model</h2>

  <p>JSON-LD is a serialization format for <a class="tref internalDFN" title="linked_data" href="#dfn-linked_data">Linked Data</a> based on JSON.
    It is therefore important to distinguish between the syntax, which is defined
    by JSON in [<cite><a class="bibref" href="#bib-RFC4627">RFC4627</a></cite>], and <dfn title="json-ld_data_model" id="dfn-json-ld_data_model">JSON-LD's data model</dfn>
    which is defined as follows:</p>

  <ul>
    <li>A <dfn title="json-ld_document" id="dfn-json-ld_document">JSON-LD document</dfn> serializes a collection of
      <a class="tref internalDFN" title="json-ld_graph" href="#dfn-json-ld_graph">JSON-LD graphs</a> and comprises exactly one
      <dfn title="default_graph" id="dfn-default_graph">default graph</dfn> and zero or more <dfn title="named_graph" id="dfn-named_graph">named graphs</dfn>.</li>
    <li>The default graph does not have a name and <em class="rfc2119" title="may">may</em> be empty.</li>
    <li>Each named graph is a pair consisting of an <a class="tref internalDFN" title="iri" href="#dfn-iri"><abbr title="Internationalized Resource Identifier">IRI</abbr></a> or <a class="tref internalDFN" title="blank_node" href="#dfn-blank_node">blank node</a>
      (the <dfn title="graph_name" id="dfn-graph_name">graph name</dfn>) and a <a class="tref internalDFN" title="json-ld_graph" href="#dfn-json-ld_graph">JSON-LD graph</a>. Whenever possible, the
      <a class="tref internalDFN" title="graph_name" href="#dfn-graph_name">graph name</a> <em class="rfc2119" title="should">should</em> be an <a class="tref internalDFN" title="iri" href="#dfn-iri"><abbr title="Internationalized Resource Identifier">IRI</abbr></a>.</li>
    <li>A <dfn title="json-ld_graph" id="dfn-json-ld_graph">JSON-LD graph</dfn> is a labeled directed graph, i.e., a set of
      <a class="tref internalDFN" title="node" href="#dfn-node">nodes</a> connected by <a class="tref internalDFN" title="edge" href="#dfn-edge">edges</a>.</li>
    <li>Every <dfn title="edge" id="dfn-edge">edge</dfn> has a direction associated with it and is labeled with
      an <a class="tref internalDFN" title="iri" href="#dfn-iri"><abbr title="Internationalized Resource Identifier">IRI</abbr></a> or a <a class="tref internalDFN" title="blank_node_identifier" href="#dfn-blank_node_identifier">blank node identifier</a>. Within the JSON-LD syntax
      these edge labels are called <dfn title="property" id="dfn-property">properties</dfn>. Whenever possible, an
      <a class="tref internalDFN" title="edge" href="#dfn-edge">edge</a> <em class="rfc2119" title="should">should</em> be labeled with an <a class="tref internalDFN" title="iri" href="#dfn-iri"><abbr title="Internationalized Resource Identifier">IRI</abbr></a>.</li>
    <li>Every <dfn title="node" id="dfn-node">node</dfn> is an <a class="tref internalDFN" title="iri" href="#dfn-iri"><abbr title="Internationalized Resource Identifier">IRI</abbr></a>, a <a class="tref internalDFN" title="blank_node" href="#dfn-blank_node">blank node</a>,
      a <a class="tref internalDFN" title="json-ld_value" href="#dfn-json-ld_value">JSON-LD value</a>, or a <a class="tref internalDFN" title="list" href="#dfn-list">list</a>.</li>
    <li>A node having an outgoing edge <em class="rfc2119" title="must">must</em> be an <a class="tref internalDFN" title="iri" href="#dfn-iri"><abbr title="Internationalized Resource Identifier">IRI</abbr></a> or a
      <a class="tref internalDFN" title="blank_node" href="#dfn-blank_node">blank node</a>.</li>
    <li>A <a class="tref internalDFN" title="json-ld_graph" href="#dfn-json-ld_graph">JSON-LD graph</a> <em class="rfc2119" title="should not">should not</em> contain unconnected <a class="tref internalDFN" title="node" href="#dfn-node">nodes</a>,
      i.e., nodes which are not connected by an <a class="tref internalDFN" title="edge" href="#dfn-edge">edge</a> to any other <a class="tref internalDFN" title="node" href="#dfn-node">node</a>.</li>
    <li>An <dfn title="iri" id="dfn-iri"><abbr title="Internationalized Resource Identifier">IRI</abbr></dfn>
      (Internationalized Resource Identifier) is a string that conforms to the syntax
      defined in [<cite><a class="bibref" href="#bib-RFC3987">RFC3987</a></cite>]. <a class="tref internalDFN" title="iri" href="#dfn-iri">IRIs</a> used within a
      <a class="tref internalDFN" title="json-ld_graph" href="#dfn-json-ld_graph">JSON-LD graph</a> <em class="rfc2119" title="should">should</em> return a <a class="tref internalDFN" title="linked_data" href="#dfn-linked_data">Linked Data</a> document describing
      the resource denoted by that <abbr title="Internationalized Resource Identifier">IRI</abbr> when being dereferenced.</li>
    <li>A <dfn title="blank_node" id="dfn-blank_node">blank node</dfn> is a <a class="tref internalDFN" title="node" href="#dfn-node">node</a> which is neither an <a class="tref internalDFN" title="iri" href="#dfn-iri"><abbr title="Internationalized Resource Identifier">IRI</abbr></a>,
      nor a <a class="tref internalDFN" title="json-ld_value" href="#dfn-json-ld_value">JSON-LD value</a>, or a <a class="tref internalDFN" title="list" href="#dfn-list">list</a>. A blank node <em class="rfc2119" title="may">may</em> be identified
      by a <a class="tref internalDFN" title="blank_node_identifier" href="#dfn-blank_node_identifier">blank node identifier</a>.</li>
    <li>A <dfn title="blank_node_identifier" id="dfn-blank_node_identifier">blank node identifier</dfn> is a string that can be used as an identifier
      for a <a class="tref internalDFN" title="blank_node" href="#dfn-blank_node">blank node</a> within the scope of a <a class="tref internalDFN" title="json-ld_document" href="#dfn-json-ld_document">JSON-LD document</a>.
      Blank node identifiers begin with <code>_:</code>.</li>
    <li>A <dfn title="json-ld_value" id="dfn-json-ld_value">JSON-LD value</dfn> is a <a class="tref internalDFN" title="string" href="#dfn-string">string</a>, a <a class="tref internalDFN" title="number" href="#dfn-number">number</a>,
      <a class="tref internalDFN" title="true" href="#dfn-true">true</a> or <a class="tref internalDFN" title="false" href="#dfn-false">false</a>, a <a class="tref internalDFN" title="typed_value" href="#dfn-typed_value">typed value</a>, or a
      <a class="tref internalDFN" title="language-tagged_string" href="#dfn-language-tagged_string">language-tagged string</a>.</li>
    <li>A <dfn title="typed_value" id="dfn-typed_value">typed value</dfn> consists of a value, which is a string, and a type, which is an <abbr title="Internationalized Resource Identifier">IRI</abbr>.</li>
    <li>A <dfn title="language-tagged_string" id="dfn-language-tagged_string">language-tagged string</dfn> consists of a string and a non-empty language
      tag as defined by [<cite><a class="bibref" href="#bib-BCP47">BCP47</a></cite>]. The language tag must be well-formed according to section
      <a href="http://tools.ietf.org/html/bcp47#section-2.2.9">2.2.9</a> of [<cite><a class="bibref" href="#bib-BCP47">BCP47</a></cite>], and <em class="rfc2119" title="must">must</em>
      be normalized to lowercase.</li>
    <li>A <dfn title="list" id="dfn-list">list</dfn> is an ordered sequence of <a class="tref internalDFN" title="iri" href="#dfn-iri">IRIs</a>,
      <a class="tref internalDFN" title="blank_node" href="#dfn-blank_node">blank nodes</a>, and
      <a class="tref internalDFN" title="json-ld_value" href="#dfn-json-ld_value">JSON-LD values</a>.</li>
  </ul>

  <div class="issue"><div class="issue-title"><span>Issue</span></div><p class="">In contrast to the RDF data model as defined in [<cite><a class="bibref" href="#bib-RDF-CONCEPTS">RDF-CONCEPTS</a></cite>], JSON-LD allows
    blank nodes as property labels and graph names. This feature is
    controversial in the RDF WG and may be removed in the future.</p></div>

  <p><a class="tref internalDFN" title="json-ld_document" href="#dfn-json-ld_document">JSON-LD documents</a> <em class="rfc2119" title="may">may</em> contain data that cannot be
    represented by the <a class="tref internalDFN" title="json-ld_data_model" href="#dfn-json-ld_data_model">data model</a> defined above.
    Unless otherwise specified, such data is ignored when a <a class="tref internalDFN" title="json-ld_document" href="#dfn-json-ld_document">JSON-LD document</a>
    is being processed. This means, e.g., that properties which are not mapped to an
    <a class="tref internalDFN" title="iri" href="#dfn-iri"><abbr title="Internationalized Resource Identifier">IRI</abbr></a> or <a class="tref internalDFN" title="blank_node" href="#dfn-blank_node">blank node</a> will be ignored.</p>

  <p style="text-align: center"><img src="linked-data-graph.png" title="An illustration of JSON-LD's data model" /></p>
  <p style="text-align: center">Figure 1: An illustration of JSON-LD's data model.</p>
</section>

<section class="appendix normative" id="json-ld-grammar">

<!--OddPage-->
<h2><span class="secno">B. </span>JSON-LD Grammar</h2>
<em>This section is normative</em>

<div class="issue"><div class="issue-title"><a href="https://github.com/json-ld/json-ld.org/issues/114"><span>Issue 114</span></a></div><p class="">This section is an attempt to formalize
a normative grammar for JSON-LD.</p></div>

<p>This appendix restates the syntactic conventions described in the
  previous sections more formally.</p>

<div class="note"><div class="note-title"><span>Note</span></div><p class="">The JSON-LD context allows <a class="tref internalDFN" title="keyword" href="#dfn-keyword">keywords</a>
  <a href="#aliasing-keywords" class="sec-ref"><span class="secno">6.13</span> <span class="sec-title">Aliasing Keywords</span></a>). Whenever a <a class="tref internalDFN" title="keyword" href="#dfn-keyword">keyword</a> is
  discussed in this grammar, the statements also apply to an alias for
  that <a class="tref internalDFN" title="keyword" href="#dfn-keyword">keyword</a>. For example, if the <a class="tref internalDFN" title="active_context" href="#dfn-active_context">active context</a>
  defines the <a class="tref internalDFN" title="term" href="#dfn-term">term</a> <code>id</code> as an alias for <code>@id</code>,
  that alias may be legitimately used as a substitution for <code>@id</code>.
  Note that <a class="tref internalDFN" title="keyword" href="#dfn-keyword">keyword</a> aliases are not expanded during context
  processing.</p></div>

<p>A <a class="tref internalDFN" title="json-ld_document" href="#dfn-json-ld_document">JSON-LD document</a> <em class="rfc2119" title="must">must</em> be a valid JSON document as described
  in [<cite><a class="bibref" href="#bib-RFC4627">RFC4627</a></cite>].</p>

<p>A <a class="tref internalDFN" title="json-ld_document" href="#dfn-json-ld_document">JSON-LD document</a> <em class="rfc2119" title="must">must</em> be a single <a class="tref internalDFN" title="node_object" href="#dfn-node_object">node object</a>
  or a JSON <a class="tref internalDFN" title="array" href="#dfn-array">array</a> containing a set of one or more
  <a class="tref internalDFN" title="node_object" href="#dfn-node_object">node objects</a>.</p>

<section id="grammar-node-object" typeof="bibo:Chapter" resource="#grammar-node-object" rel="bibo:chapter">
<h3><span class="secno">B.1 </span>Node Object</h3>

<p>A <dfn title="node_object" id="dfn-node_object">node object</dfn> represents zero or more properties of a
  <a class="tref internalDFN" title="node" href="#dfn-node">node</a> in the <a class="tref internalDFN" title="json-ld_graph" href="#dfn-json-ld_graph">JSON-LD graph</a> serialized by the
  <a class="tref internalDFN" title="json-ld_document" href="#dfn-json-ld_document">JSON-LD document</a>.

  A <a class="tref internalDFN" title="json_object" href="#dfn-json_object">JSON Object</a> is a <a class="tref internalDFN" title="node_object" href="#dfn-node_object">node object</a> if
  it exists outside of the JSON-LD Context and:</p>

  <ul>
    <li>it does not contain the <code>@value</code>, <code>@list</code>,
    <code>@annotation</code>, or <code>@set</code> keywords, or</li>
    <li>it does not contain the <code>@graph</code> keyword and is
    the top-most <a class="tref internalDFN" title="json_object" href="#dfn-json_object">JSON Object</a> in the JSON-LD document.
  </li></ul>

  The properties of a <a class="tref internalDFN" title="node" href="#dfn-node">node</a> in the <a class="tref internalDFN" title="json-ld_graph" href="#dfn-json-ld_graph">JSON-LD graph</a>
  may be spread among different <a class="tref internalDFN" title="node_object" href="#dfn-node_object">node objects</a>
  within a document. When that happens,
  the keys of the different <a class="tref internalDFN" title="node_object" href="#dfn-node_object">node objects</a>
  are merged to create the properties of the resulting <a class="tref internalDFN" title="node" href="#dfn-node">node</a>.<p></p>

<p>A <a class="tref internalDFN" title="node_object" href="#dfn-node_object">node object</a> <em class="rfc2119" title="must">must</em> be a <a class="tref internalDFN" title="json_object" href="#dfn-json_object">JSON object</a> that contains
  one or more key-value pairs. Keys <em class="rfc2119" title="must">must</em> either be
  <a class="tref internalDFN" title="iri" href="#dfn-iri">IRIs</a>,
  <a class="tref internalDFN" title="compact_iri" href="#dfn-compact_iri">compact IRIs</a>,
  <a class="tref internalDFN" title="term" href="#dfn-term">terms</a> valid in the <a class="tref internalDFN" title="active_context" href="#dfn-active_context">active context</a>, or
  one of the following <a class="tref internalDFN" title="keyword" href="#dfn-keyword">keywords</a>:</p>
<ul>
  <li><code>@context</code>,</li>
  <li><code>@graph</code>,</li>
  <li><code>@id</code>, or</li>
  <li><code>@type</code></li>
</ul>
<p>If the <a class="tref internalDFN" title="node_object" href="#dfn-node_object">node object</a> contains the <code>@context</code>
  key, its value <em class="rfc2119" title="must">must</em> be one of the following:</p>
<ul>
  <li>an <a class="tref internalDFN" title="iri" href="#dfn-iri"><abbr title="Internationalized Resource Identifier">IRI</abbr></a>,</li>
  <li>a <a class="tref internalDFN" title="context_definition" href="#dfn-context_definition">context definition</a>, or</li>
  <li>an <a class="tref internalDFN" title="array" href="#dfn-array">array</a> composed of any number of the previous two expressions.</li>
</ul>

<p>If the <a class="tref internalDFN" title="node_object" href="#dfn-node_object">node object</a> contains the <code>@id</code> key, 
  its value <em class="rfc2119" title="must">must</em> be
  an <a class="tref internalDFN" title="iri" href="#dfn-iri"><abbr title="Internationalized Resource Identifier">IRI</abbr></a>,
  a <a class="tref internalDFN" title="compact_iri" href="#dfn-compact_iri">compact <abbr title="Internationalized Resource Identifier">IRI</abbr></a> (including <a class="tref internalDFN" title="blank_node_identifier" href="#dfn-blank_node_identifier">blank node identifiers</a>), or
  a <a class="tref internalDFN" title="term" href="#dfn-term">term</a> defined in the <a class="tref internalDFN" title="active_context" href="#dfn-active_context">active context</a> expanding
  into an <a class="tref internalDFN" title="iri" href="#dfn-iri"><abbr title="Internationalized Resource Identifier">IRI</abbr></a> or a <a class="tref internalDFN" title="blank_node_identifier" href="#dfn-blank_node_identifier">blank node identifier</a>.
  See <a href="#node-identifiers" class="sec-ref"><span class="secno">5.4</span> <span class="sec-title">Node Identifiers</span></a>, <a href="#compact-iris" class="sec-ref"><span class="secno">6.1</span> <span class="sec-title">Compact IRIs</span></a>,
  and <a href="#identifying-blank-nodes" class="sec-ref"><span class="secno">6.12</span> <span class="sec-title">Identifying Blank Nodes</span></a> for further discussion on
  <code>@id</code> values.</p>

<p>If the <a class="tref internalDFN" title="node_object" href="#dfn-node_object">node object</a> contains the <code>@type</code>
  key, its value <em class="rfc2119" title="must">must</em> be either
  an <a class="tref internalDFN" title="absolute_iri" href="#dfn-absolute_iri">absolute <abbr title="Internationalized Resource Identifier">IRI</abbr></a>,
  a <a class="tref internalDFN" title="compact_iri" href="#dfn-compact_iri">compact <abbr title="Internationalized Resource Identifier">IRI</abbr></a> (excluding <a class="tref internalDFN" title="blank_node_identifier" href="#dfn-blank_node_identifier">blank node identifier</a>),
  a <a class="tref internalDFN" title="term" href="#dfn-term">term</a> defined in the <a class="tref internalDFN" title="active_context" href="#dfn-active_context">active context</a> expanding into an <a class="tref internalDFN" title="absolute_iri" href="#dfn-absolute_iri">absolute <abbr title="Internationalized Resource Identifier">IRI</abbr></a>, or
  an <a class="tref internalDFN" title="array" href="#dfn-array">array</a> of any of these.
  See <a href="#specifying-the-type" class="sec-ref"><span class="secno">5.5</span> <span class="sec-title">Specifying the Type</span></a> for further discussion on
  <code>@type</code> values.</p>

<p>If the <a class="tref internalDFN" title="node_object" href="#dfn-node_object">node object</a> contains the <code>@graph</code>
  key, its value <em class="rfc2119" title="must">must</em> be
  a <a class="tref internalDFN" title="node_object" href="#dfn-node_object">node object</a> or
  an <a class="tref internalDFN" title="array" href="#dfn-array">array</a> of zero or more <a class="tref internalDFN" title="node_object" href="#dfn-node_object">node objects</a>.
  If the <a class="tref internalDFN" title="node_object" href="#dfn-node_object">node object</a> contains an <code>@id</code> keyword,
  its value is used as the label of a named graph.
  See <a href="#named-graphs" class="sec-ref"><span class="secno">6.11</span> <span class="sec-title">Named Graphs</span></a> for further discussion on
  <code>@graph</code> values.</p>

<div class="note"><div class="note-title"><span>Note</span></div><p class="">As a special case, if a <a class="tref internalDFN" title="json_object" href="#dfn-json_object">JSON object</a> contains no
  keys other than <code>@graph</code> and <code>@context</code>, and the
  <a class="tref internalDFN" title="json_object" href="#dfn-json_object">JSON object</a> is the root of the JSON-LD document, the
  <a class="tref internalDFN" title="json_object" href="#dfn-json_object">JSON object</a> is not treated as a <a class="tref internalDFN" title="node_object" href="#dfn-node_object">node object</a>; this
  is used as a way of defining <a class="tref internalDFN" title="node_object" href="#dfn-node_object">node
  definitions</a> that may not form a connected graph. This allows a
  <a class="tref internalDFN" title="context" href="#dfn-context">context</a> to be defined which is shared by all of the constituent
  <a class="tref internalDFN" title="node_object" href="#dfn-node_object">node objects</a>.</p></div>

<p>A <a class="tref internalDFN" title="json-ld_document" href="#dfn-json-ld_document">JSON-LD document</a> <em class="rfc2119" title="must not">must not</em> contain any <a class="tref internalDFN" title="keyword" href="#dfn-keyword">keyword</a> 
  that expands to another keyword.</p>

<!-- 
  tidoust: clarify?  
  msporny: This restriction prevents confusing JSON-LD Contexts where, 
  for example, @id is an alias for @type, thus preventing the use of 
  @id altogether. The previous text said "or alias", which I believe was an
  error, so I removed it.
-->


<p>Keys in a <a class="tref internalDFN" title="node_object" href="#dfn-node_object">node object</a> that are not
  <a class="tref internalDFN" title="keyword" href="#dfn-keyword">keywords</a> <em class="rfc2119" title="must">must</em> expand to an <a class="tref internalDFN" title="absolute_iri" href="#dfn-absolute_iri">absolute <abbr title="Internationalized Resource Identifier">IRI</abbr></a>
  using the <a class="tref internalDFN" title="active_context" href="#dfn-active_context">active context</a>. The values associated with these keys
  <em class="rfc2119" title="must">must</em> be one of the following:</p>

<ul>
  <li><a class="tref internalDFN" title="string" href="#dfn-string">string</a>,</li>
  <li><a class="tref internalDFN" title="number" href="#dfn-number">number</a>,</li>
  <li><a class="tref internalDFN" title="true" href="#dfn-true">true</a>,</li>
  <li><a class="tref internalDFN" title="false" href="#dfn-false">false</a>,</li>
  <li><a class="tref internalDFN" title="null" href="#dfn-null">null</a>,</li>
  <li><a class="tref internalDFN" title="node_object" href="#dfn-node_object">node object</a>,</li>
  <li><a class="tref internalDFN" title="expanded_typed_value" href="#dfn-expanded_typed_value">expanded typed value</a>,</li>
  <li><a class="tref internalDFN" title="expanded_language-tagged_string" href="#dfn-expanded_language-tagged_string">expanded language-tagged string</a>,</li>
  <li><a class="tref internalDFN" title="list" href="#dfn-list">list</a> or <a class="tref internalDFN" title="set" href="#dfn-set">set</a>,</li>
  <li>an <a class="tref internalDFN" title="array" href="#dfn-array">array</a> of zero or more of the possibilities above,</li>
  <li>a <a class="tref internalDFN" title="language_map" href="#dfn-language_map">language map</a>, or </li>
  <li>an <a class="tref internalDFN" title="annotation_map" href="#dfn-annotation_map">annotation map</a></li>
</ul>

</section>

<section id="grammar-term-reference" typeof="bibo:Chapter" resource="#grammar-term-reference" rel="bibo:chapter">
  <h3><span class="secno">B.2 </span>Term</h3>
  <p>A <dfn title="term" id="dfn-term">term</dfn> is a short-hand <a class="tref internalDFN" title="string" href="#dfn-string">string</a> that expands
    to an <a class="tref internalDFN" title="iri" href="#dfn-iri"><abbr title="Internationalized Resource Identifier">IRI</abbr></a> or a <a class="tref internalDFN" title="blank_node_identifier" href="#dfn-blank_node_identifier">blank node identifier</a>.</p>

  <p>A <a class="tref internalDFN" title="term" href="#dfn-term">term</a> <em class="rfc2119" title="must not">must not</em> equal any of the JSON-LD
    <a class="tref internalDFN" title="keyword" href="#dfn-keyword">keywords</a>.</p>

  <p>To avoid forward-compatibility issues, a <a class="tref internalDFN" title="term" href="#dfn-term">term</a> <em class="rfc2119" title="should not">should not</em> start
    with an <code>@</code> character as future versions of JSON-LD may introduce
    additional <a class="tref internalDFN" title="keyword" href="#dfn-keyword">keywords</a>. Furthermore, the use of
    empty terms (<code>&quot;&quot;</code>) is discouraged as not all programming languages
    are able to handle empty property names.</p>

  <p>See <a href="#the-context" class="sec-ref"><span class="secno">5.1</span> <span class="sec-title">The Context</span></a> and <a href="#iris" class="sec-ref"><span class="secno">5.3</span> <span class="sec-title">IRIs</span></a> for further discussion
    on mapping <a class="tref internalDFN" title="term" href="#dfn-term">terms</a> to <a class="tref internalDFN" title="iri" href="#dfn-iri">IRIs</a>.</p>
</section>

<section id="grammar-language-map" typeof="bibo:Chapter" resource="#grammar-language-map" rel="bibo:chapter">
<h3><span class="secno">B.3 </span>Language Map</h3>
<p>A <dfn title="language_map" id="dfn-language_map">language map</dfn> is used to associate a language with a value in a
  way that allows easy programmatic access. A <a class="tref internalDFN" title="language_map" href="#dfn-language_map">language map</a> may be
  used as a term value within a <a class="tref internalDFN" title="node_object" href="#dfn-node_object">node object</a> if the term is defined
  with <code>@container</code> set to <code>@language</code>. The keys of a
  <a class="tref internalDFN" title="language_map" href="#dfn-language_map">language map</a> <em class="rfc2119" title="must">must</em> be lowercase [<cite><a class="bibref" href="#bib-BCP47">BCP47</a></cite>]
  <a class="tref internalDFN" title="string" href="#dfn-string">strings</a> with an associated value that is any
  of the following types:</p>
<ul>
  <li><a class="tref internalDFN" title="string" href="#dfn-string">string</a>, or</li>
  <li>an <a class="tref internalDFN" title="array" href="#dfn-array">array</a> of zero or more strings</li>
</ul>
<p>See <a href="#language-tagged-strings" class="sec-ref"><span class="secno">6.3</span> <span class="sec-title">Language-tagged Strings</span></a> for further discussion on language maps.</p>
</section>

<section id="grammar-annotation-map" typeof="bibo:Chapter" resource="#grammar-annotation-map" rel="bibo:chapter">
<h3><span class="secno">B.4 </span>Annotation Map</h3>
<p>An <dfn title="annotation_map" id="dfn-annotation_map">annotation map</dfn> allows keys that have no semantic meaning, 
  but should be preserved regardless, to be used in JSON-LD documents. 
  An <a class="tref internalDFN" title="annotation_map" href="#dfn-annotation_map">annotation map</a> may 
  be used as a <a class="tref internalDFN" title="term" href="#dfn-term">term</a> value within a <a class="tref internalDFN" title="node_object" href="#dfn-node_object">node object</a> if the 
  term is defined with <code>@container</code> set to <code>@annotation</code>. 
  The keys of a <a class="tref internalDFN" title="annotation_map" href="#dfn-annotation_map">annotation map</a> <em class="rfc2119" title="must">must</em> be 
  <a class="tref internalDFN" title="string" href="#dfn-string">strings</a> with an associated value that is any
  of the following types:</p>
<ul>
  <li><a class="tref internalDFN" title="string" href="#dfn-string">string</a>,</li>
  <li><a class="tref internalDFN" title="number" href="#dfn-number">number</a>,</li>
  <li><a class="tref internalDFN" title="true" href="#dfn-true">true</a>,</li>
  <li><a class="tref internalDFN" title="false" href="#dfn-false">false</a>,</li>
  <li><a class="tref internalDFN" title="null" href="#dfn-null">null</a>,</li>
  <li><a class="tref internalDFN" title="node_object" href="#dfn-node_object">node object</a>,</li>
  <li><a class="tref internalDFN" title="expanded_value" href="#dfn-expanded_value">expanded value</a>,</li>
  <li>an <a class="tref internalDFN" title="array" href="#dfn-array">array</a> of zero or more of the above possibilities</li>
</ul>
<p>See <a href="#data-annotations" class="sec-ref"><span class="secno">6.14</span> <span class="sec-title">Data Annotations</span></a> for further information on this 
topic.</p>
</section>

<section id="grammar-expanded-values" typeof="bibo:Chapter" resource="#grammar-expanded-values" rel="bibo:chapter">
<h3><span class="secno">B.5 </span>Expanded Values</h3>

<p>An <dfn title="expanded_value" id="dfn-expanded_value">expanded value</dfn> is used to explicitly associate a type or a
  language with a value to create a <a class="tref internalDFN" title="typed_value" href="#dfn-typed_value">typed value</a> or a <a class="tref internalDFN" title="language-tagged_string" href="#dfn-language-tagged_string">language-tagged
  string</a>.</p>

<p>An <a class="tref internalDFN" title="expanded_value" href="#dfn-expanded_value">expanded value</a> <em class="rfc2119" title="must">must</em> be a <a class="tref internalDFN" title="json_object" href="#dfn-json_object">JSON object</a> containing the
  <code>@value</code> key. It <em class="rfc2119" title="may">may</em> also contain a <code>@type</code> or
  a <code>@language</code> key but <em class="rfc2119" title="must not">must not</em> contain both a <code>@type</code>
  and a <code>@language</code> key. An <a class="tref internalDFN" title="expanded_value" href="#dfn-expanded_value">expanded value</a> <em class="rfc2119" title="must not">must not</em>
  contain keys other than <code>@value</code>, <code>@language</code>, and
  <code>@type</code>. An <a class="tref internalDFN" title="expanded_value" href="#dfn-expanded_value">expanded value</a> that contains a
  <code>@type</code> key is called an <dfn title="expanded_typed_value" id="dfn-expanded_typed_value">expanded typed value</dfn>.
  An <a class="tref internalDFN" title="expanded_value" href="#dfn-expanded_value">expanded value</a> that contains a <code>@language</code> key
  is called an <dfn title="expanded_language-tagged_string" id="dfn-expanded_language-tagged_string">expanded language-tagged string</dfn>.</p>

<p>The value associated with the <code>@value</code> key <em class="rfc2119" title="must">must</em> be either a
  <a class="tref internalDFN" title="string" href="#dfn-string">string</a>, <a class="tref internalDFN" title="number" href="#dfn-number">number</a>, <a class="tref internalDFN" title="true" href="#dfn-true">true</a>, 
  <a class="tref internalDFN" title="false" href="#dfn-false">false</a> or <a class="tref internalDFN" title="null" href="#dfn-null">null</a>.</p>

<p>The value associated with the <code>@language</code> key <em class="rfc2119" title="must">must</em> have the 
  lexical form described in [<cite><a class="bibref" href="#bib-BCP47">BCP47</a></cite>], or be <a class="tref internalDFN" title="null" href="#dfn-null">null</a>.</p>

<p>The value associated with the <code>@annotation</code> key <em class="rfc2119" title="must">must</em> be a 
  <a class="tref internalDFN" title="string" href="#dfn-string">string</a>.</p>

<p>The value associated with the <code>@type</code> key <em class="rfc2119" title="must">must</em> be a 
  <a class="tref internalDFN" title="term" href="#dfn-term">term</a>, a <a class="tref internalDFN" title="compact_iri" href="#dfn-compact_iri">compact <abbr title="Internationalized Resource Identifier">IRI</abbr></a>,
  an <a class="tref internalDFN" title="absolute_iri" href="#dfn-absolute_iri">absolute <abbr title="Internationalized Resource Identifier">IRI</abbr></a>, or <code>null</code>.</p>

<p>See <a href="#typed-values" class="sec-ref"><span class="secno">6.2</span> <span class="sec-title">Typed Values</span></a> and <a href="#language-tagged-strings" class="sec-ref"><span class="secno">6.3</span> <span class="sec-title">Language-tagged Strings</span></a>
  for more information on
  <a class="tref internalDFN" title="expanded_value" href="#dfn-expanded_value">expanded values</a>.</p>
</section>

<section id="grammar-set-list" typeof="bibo:Chapter" resource="#grammar-set-list" rel="bibo:chapter">
<h3><span class="secno">B.6 </span>List and Set Values</h3>

<p>A <a class="tref internalDFN" title="list" href="#dfn-list">list</a> represents an <em>ordered</em> set of values.
  A <dfn title="set" id="dfn-set">set</dfn> represents an <em>unordered</em> set of values.
  Unless otherwise specified (typically through the use of a <a class="tref internalDFN" title="list" href="#dfn-list">list</a>),
  <a class="tref internalDFN" title="array" href="#dfn-array">arrays</a> are unordered in JSON-LD. As such, the
  <code>@set</code> keyword, when used in the body of a JSON-LD document,
  represents just syntactic sugar which is optimized away when processing the document.
  However, it is very helpful when used within the context of a document. Values
  of terms associated with a <code>@set</code> or <code>@list</code> container
  will always be represented in the form of an array when a document is processed -
  even if there is just a single value that would otherwise be optimized to
  a non-array form in <a href="#compact-document-form">compact document form</a>.
  This simplifies post-processing of the data as the data is always in array form.</p>

<p>A <a class="tref internalDFN" title="list" href="#dfn-list">list</a> <em class="rfc2119" title="must">must</em> be a <a class="tref internalDFN" title="json_object" href="#dfn-json_object">JSON object</a> that contains a single key-value pair where the key is <code>@list</code>.</p>

<p>A <a class="tref internalDFN" title="set" href="#dfn-set">set</a> <em class="rfc2119" title="must">must</em> be a <a class="tref internalDFN" title="json_object" href="#dfn-json_object">JSON object</a> that contains a single key-value pair where the key is <code>@set</code>.</p>

<p>In both cases, the value associated with the key <em class="rfc2119" title="must">must</em> be an <a class="tref internalDFN" title="array" href="#dfn-array">array</a> of any of the following:</p>
<ul>
  <li><a class="tref internalDFN" title="string" href="#dfn-string">string</a>,</li>
  <li><a class="tref internalDFN" title="number" href="#dfn-number">number</a>,</li>
  <li><a class="tref internalDFN" title="true" href="#dfn-true">true</a>,</li>
  <li><a class="tref internalDFN" title="false" href="#dfn-false">false</a>,</li>
  <li><a class="tref internalDFN" title="null" href="#dfn-null">null</a>,</li>
  <li><a class="tref internalDFN" title="node_object" href="#dfn-node_object">node object</a>,</li>
  <li><a class="tref internalDFN" title="expanded_typed_value" href="#dfn-expanded_typed_value">expanded typed value</a>, or</li>
  <li><a class="tref internalDFN" title="expanded_language-tagged_string" href="#dfn-expanded_language-tagged_string">expanded language-tagged string</a></li>
</ul>

<p>See <a href="#sets-and-lists" class="sec-ref"><span class="secno">6.9</span> <span class="sec-title">Sets and Lists</span></a> for further discussion on List and Set Values.</p>
</section>

<section id="grammar-context" typeof="bibo:Chapter" resource="#grammar-context" rel="bibo:chapter">
<h3><span class="secno">B.7 </span>Context Definition</h3>
<p>A <dfn title="context_definition" id="dfn-context_definition">context definition</dfn> defines a <a class="tref internalDFN" title="local_context" href="#dfn-local_context">local context</a> in a <a class="tref internalDFN" title="node_object" href="#dfn-node_object">node object</a>.</p>

<p>A <a class="tref internalDFN" title="context_definition" href="#dfn-context_definition">context definition</a> <em class="rfc2119" title="must">must</em> be a <a class="tref internalDFN" title="json_object" href="#dfn-json_object">JSON object</a>
  containing one or more key-value pairs. Keys <em class="rfc2119" title="must">must</em> either be
  <a class="tref internalDFN" title="term" href="#dfn-term">terms</a> or <code>@language</code> or <code>@vocab</code> <a class="tref internalDFN" title="keyword" href="#dfn-keyword">keywords</a>.

</p><p>If the <a class="tref internalDFN" title="context_definition" href="#dfn-context_definition">context definition</a> has a <code>@language</code> key,
  its value <em class="rfc2119" title="must">must</em> have the lexical form described in [<cite><a class="bibref" href="#bib-BCP47">BCP47</a></cite>] or be <a class="tref internalDFN" title="null" href="#dfn-null">null</a>.</p>
<p>If the <a class="tref internalDFN" title="context_definition" href="#dfn-context_definition">context definition</a> has a <code>@vocab</code> key,
  its value <em class="rfc2119" title="must">must</em> have the lexical form of <a class="tref internalDFN" title="absolute_iri" href="#dfn-absolute_iri">absolute <abbr title="Internationalized Resource Identifier">IRI</abbr></a> or be <a class="tref internalDFN" title="null" href="#dfn-null">null</a>.</p>

<p><a class="tref internalDFN" title="term" href="#dfn-term">Term</a> values <em class="rfc2119" title="must">must</em> be either a
  <a class="tref internalDFN" title="string" href="#dfn-string">string</a>, <code>null</code>, or an <a class="tref internalDFN" title="expanded_term_definition" href="#dfn-expanded_term_definition">expanded term definition</a>.</p>

<p>An <dfn title="expanded_term_definition" id="dfn-expanded_term_definition">expanded term definition</dfn> is used to describe the mapping
  between a <a class="tref internalDFN" title="term" href="#dfn-term">term</a> and its expanded identifier, as well as other
  properties of the value associated with the <a class="tref internalDFN" title="term" href="#dfn-term">term</a> when it is
  used as key in a <a class="tref internalDFN" title="node_object" href="#dfn-node_object">node object</a>.</p>

<p>An <a class="tref internalDFN" title="expanded_term_definition" href="#dfn-expanded_term_definition">expanded term definition</a> <em class="rfc2119" title="should">should</em> be a <a class="tref internalDFN" title="json_object" href="#dfn-json_object">JSON object</a>
  composed of zero or more keys from <code>@id</code>,
  <code>@type</code>, <code>@language</code> or <code>@container</code>. An
  <a class="tref internalDFN" title="expanded_term_definition" href="#dfn-expanded_term_definition">expanded term definition</a> <em class="rfc2119" title="should not">should not</em> contain any other keys. 
</p><p>If the <a class="tref internalDFN" title="term" href="#dfn-term">term</a> definition is not <code>null</code>, a <a class="tref internalDFN" title="compact_iri" href="#dfn-compact_iri">compact <abbr title="Internationalized Resource Identifier">IRI</abbr></a>, or an <a class="tref internalDFN" title="absolute_iri" href="#dfn-absolute_iri">absolute <abbr title="Internationalized Resource Identifier">IRI</abbr></a>,
  the <a class="tref internalDFN" title="expanded_term_definition" href="#dfn-expanded_term_definition">expanded term
  definition</a> <em class="rfc2119" title="must">must</em> include the <code>@id</code> key.</p>

<p>If the <a class="tref internalDFN" title="expanded_term_definition" href="#dfn-expanded_term_definition">expanded term definition</a> contains the <code>@id</code> <a class="tref internalDFN" title="keyword" href="#dfn-keyword">keyword</a>,
  its value <em class="rfc2119" title="must">must</em> be <code>null</code>, an <a class="tref internalDFN" title="iri" href="#dfn-iri"><abbr title="Internationalized Resource Identifier">IRI</abbr></a>, a <a class="tref internalDFN" title="compact_iri" href="#dfn-compact_iri">compact <abbr title="Internationalized Resource Identifier">IRI</abbr></a>, a <a class="tref internalDFN" title="term" href="#dfn-term">term</a> defined in the defining <a class="tref internalDFN" title="context_definition" href="#dfn-context_definition">context definition</a> or the <a class="tref internalDFN" title="active_context" href="#dfn-active_context">active context</a>, or an <a class="tref internalDFN" title="array" href="#dfn-array">array</a> composed of any of the previous allowed values.</p>
<p>If the <a class="tref internalDFN" title="expanded_term_definition" href="#dfn-expanded_term_definition">expanded term definition</a> contains the <code>@type</code> <a class="tref internalDFN" title="keyword" href="#dfn-keyword">keyword</a>,
  its value <em class="rfc2119" title="must">must</em> be an <a class="tref internalDFN" title="absolute_iri" href="#dfn-absolute_iri">absolute <abbr title="Internationalized Resource Identifier">IRI</abbr></a>, a <a class="tref internalDFN" title="compact_iri" href="#dfn-compact_iri">compact <abbr title="Internationalized Resource Identifier">IRI</abbr></a>, a <a class="tref internalDFN" title="term" href="#dfn-term">term</a> defined in the defining <a class="tref internalDFN" title="context_definition" href="#dfn-context_definition">context definition</a> or the <a class="tref internalDFN" title="active_context" href="#dfn-active_context">active context</a>, or the <code>@id</code> <a class="tref internalDFN" title="keyword" href="#dfn-keyword">keyword</a>.</p>
<p>If the <a class="tref internalDFN" title="expanded_term_definition" href="#dfn-expanded_term_definition">expanded term definition</a> contains the <code>@language</code> <a class="tref internalDFN" title="keyword" href="#dfn-keyword">keyword</a>,
  its value <em class="rfc2119" title="must">must</em> have the lexical form described in [<cite><a class="bibref" href="#bib-BCP47">BCP47</a></cite>] or be <a class="tref internalDFN" title="null" href="#dfn-null">null</a>.</p>
<p>If the <a class="tref internalDFN" title="expanded_term_definition" href="#dfn-expanded_term_definition">expanded term definition</a> contains the <code>@container</code> <a class="tref internalDFN" title="keyword" href="#dfn-keyword">keyword</a>,
  its value <em class="rfc2119" title="must">must</em> be either <code>@list</code>, <code>@set</code>, <code>@language</code>, <code>@annotation</code>, or be <a class="tref internalDFN" title="null" href="#dfn-null">null</a>.
  If the value is <code>@language</code>, when the <a class="tref internalDFN" title="term" href="#dfn-term">term</a> is used outside of the <code>@context</code>, the
  associated value <em class="rfc2119" title="must">must</em> be a <a class="tref internalDFN" title="language_map" href="#dfn-language_map">language map</a>. If the value is 
  <code>@annotation</code>, when the <a class="tref internalDFN" title="term" href="#dfn-term">term</a> is used outside of 
  the <code>@context</code>, the associated value <em class="rfc2119" title="must">must</em> be an 
  <a class="tref internalDFN" title="annotation_map" href="#dfn-annotation_map">annotation map</a>.</p>

<p><a class="tref internalDFN" title="term" href="#dfn-term">Terms</a> <em class="rfc2119" title="must not">must not</em> be used in a circular manner. That is, the definition of a term cannot depend on the definition of another term if that other term also depends on the first term.</p>

<p>See <a href="#the-context" class="sec-ref"><span class="secno">5.1</span> <span class="sec-title">The Context</span></a> and <a href="#expanded-term-definition" class="sec-ref"><span class="secno">6.5</span> <span class="sec-title">Expanded Term Definition</span></a>
  for further discussion on contexts.</p>
</section>

</section>

<section class="appendix normative" id="relationship-to-rdf">
  
<!--OddPage-->
<h2><span class="secno">C. </span>Relationship to RDF</h2>

  <p>The RDF data model, as outlined in [<cite><a class="bibref" href="#bib-RDF-CONCEPTS">RDF-CONCEPTS</a></cite>], is an abstract syntax for
    representing a directed graph of information. It is a subset of
    <a class="tref internalDFN" title="json-ld_data_model" href="#dfn-json-ld_data_model">JSON-LD's data model</a> with a few
    additional constraints. The differences between the two data models are:</p>

  <ul>
    <li>In JSON-LD <a class="tref internalDFN" title="graph_name" href="#dfn-graph_name">graph names</a> can be
      <a class="tref internalDFN" title="iri" href="#dfn-iri">IRIs</a> or <a class="tref internalDFN" title="blank_node" href="#dfn-blank_node">blank nodes</a>
      whereas in RDF graph names have to be <a class="tref internalDFN" title="iri" href="#dfn-iri">IRIs</a>.</li>
    <li>In JSON-LD <a class="tref internalDFN" title="property" href="#dfn-property">properties</a> can be
      <a class="tref internalDFN" title="iri" href="#dfn-iri">IRIs</a> or <a class="tref internalDFN" title="blank_node" href="#dfn-blank_node">blank nodes</a>
      whereas in RDF properties (predicates) have to be
      <a class="tref internalDFN" title="iri" href="#dfn-iri">IRIs</a>.</li>
    <li>In contrast to RDF graphs <a class="tref internalDFN" title="json-ld_graph" href="#dfn-json-ld_graph">JSON-LD graphs</a>
      support unconnected <a class="tref internalDFN" title="node" href="#dfn-node">nodes</a>, i.e., nodes which are not
      connected to any other node.</li>
    <li>In JSON-LD lists are part of the data model whereas in RDF they are part of
      a vocabulary, namely [<cite><a class="bibref" href="#bib-RDF-SCHEMA">RDF-SCHEMA</a></cite>].</li>
    <li>RDF values are either typed <em>literals</em>
      (<a class="tref internalDFN" title="typed_value" href="#dfn-typed_value">typed values</a>) or <em>language-tagged strings</em>
      (<a class="tref internalDFN" title="language-tagged_string" href="#dfn-language-tagged_string">language-tagged strings</a>) whereas
      JSON-LD also supports JSON's native data types, i.e., <a class="tref internalDFN" title="number" href="#dfn-number">number</a>,
      <a class="tref internalDFN" title="string" href="#dfn-string">strings</a>, and the boolean values <a class="tref internalDFN" title="true" href="#dfn-true">true</a>
      and <a class="tref internalDFN" title="false" href="#dfn-false">false</a>. The JSON-LD API [<cite><a class="bibref" href="#bib-JSON-LD-API">JSON-LD-API</a></cite>] specification defines
      the conversion rules between JSON's native data types and RDF's counterparts to
      allow full round-tripping.</li>

  </ul>

  <p>Summarized these differences mean that JSON-LD is capable of serializing any RDF
    graph or dataset and most, but not all, JSON-LD documents can be transformed to RDF.
    A complete description of the algorithms to convert from RDF to JSON-LD and from
    JSON-LD to RDF is included in the JSON-LD API [<cite><a class="bibref" href="#bib-JSON-LD-API">JSON-LD-API</a></cite>] specification.</p>

  <p>Even though JSON-LD serializes RDF datasets, it can also be used as a RDF graph source.
    In that case, a consumer <em class="rfc2119" title="must">must</em> only use the default graph and ignore all named graphs.
    This allows servers to expose data in, e.g., both Turtle and JSON-LD using content
    negotiation.</p>

  <div class="note"><div class="note-title"><span>Note</span></div><p class="">Publishers supporting both dataset and graph syntaxes have to ensure that
    the primary data is stored in the default graph to enable consumers that do not support
    datasets to process the information.</p></div>
</section>

<section class="appendix informative" id="relationship-to-other-linked-data-formats">

<!--OddPage-->
<h2><span class="secno">D. </span>Relationship to Other Linked Data Formats</h2><p><em>This section is non-normative.</em></p>

<p>The JSON-LD markup examples below demonstrate how JSON-LD can be used to
  express semantic data marked up in other linked data formats such as Turtle,
  RDFa, Microformats, and Microdata. These sections are merely provided as
  evidence that JSON-LD is very flexible in what it can express across different
  <a class="tref internalDFN" title="linked_data" href="#dfn-linked_data">Linked Data</a> approaches.</p>

<section id="turtle">
  <h3><span class="secno">D.1 </span>Turtle</h3><p><em>This section is non-normative.</em></p>

  <p>The following are examples of converting RDF expressed in [<cite><a class="bibref" href="#bib-TURTLE-TR">TURTLE-TR</a></cite>]
    into JSON-LD.</p>

<section id="prefix-definitions">
<h4><span class="secno">D.1.1 </span>Prefix definitions</h4><p><em>This section is non-normative.</em></p>
<p>The JSON-LD context has direct equivalents for the Turtle
  <code>@prefix</code> declaration:</p>

<div class="example"><div class="example-title"><span>Example 61</span>: A set of statements serialized in Turtle</div><pre class="example">@prefix foaf: &lt;http://xmlns.com/foaf/0.1/&gt; .

&lt;http://manu.sporny.org/i/public&gt; a foaf:Person;
  foaf:name &quot;Manu Sporny&quot;;
  foaf:homepage &lt;http://manu.sporny.org/&gt; .</pre></div>

<div class="example"><div class="example-title"><span>Example 62</span>: The same set of statements serialized in JSON-LD</div><pre class="example">{
  &quot;@context&quot;:
  {
    &quot;foaf&quot;: &quot;http://xmlns.com/foaf/0.1/&quot;
  },
  &quot;@id&quot;: &quot;http://manu.sporny.org/i/public&quot;,
  &quot;@type&quot;: &quot;foaf:Person&quot;,
  &quot;foaf:name&quot;: &quot;Manu Sporny&quot;,
  &quot;foaf:homepage&quot;: { &quot;@id&quot;: &quot;http://manu.sporny.org/&quot; }
}</pre></div>

<div class="note"><div class="note-title"><span>Note</span></div><p class="">JSON-LD has no equivalent for the Turtle <code>@base</code> declaration.</p></div>

</section>

<section id="embedding-1">
<h4><span class="secno">D.1.2 </span>Embedding</h4>
<p>Both Turtle and JSON-LD allow embedding, although Turtle only allows embedding of
  <a class="tref internalDFN" title="blank_node" href="#dfn-blank_node">blank nodes</a>.</p>
</section>

<div class="example"><div class="example-title"><span>Example 63</span>: Embedding in Turtle</div><pre class="example">@prefix foaf: &lt;http://xmlns.com/foaf/0.1/&gt; .

&lt;http://manu.sporny.org/i/public&gt;
  a foaf:Person;
  foaf:name &quot;Manu Sporny&quot;;
  foaf:knows [ a foaf:Person; foaf:name &quot;Gregg Kellogg&quot; ] .</pre></div>

<div class="example"><div class="example-title"><span>Example 64</span>: Same embedding example in JSON-LD</div><pre class="example">{
  &quot;@context&quot;:
  {
    &quot;foaf&quot;: &quot;http://xmlns.com/foaf/0.1/&quot;
  },
  &quot;@id&quot;: &quot;http://manu.sporny.org/i/public&quot;,
  &quot;@type&quot;: &quot;foaf:Person&quot;,
  &quot;foaf:name&quot;: &quot;Manu Sporny&quot;,
  &quot;foaf:knows&quot;:
  {
    &quot;@type&quot;: &quot;foaf:Person&quot;,
    &quot;foaf:name&quot;: &quot;Gregg Kellogg&quot;
  }
}</pre></div>
<section id="lists">
<h4><span class="secno">D.1.3 </span>Lists</h4>
<p>Both JSON-LD and Turtle can represent sequential lists of values.</p>

<div class="example"><div class="example-title"><span>Example 65</span>: A list of values in Turtle</div><pre class="example">@prefix foaf: &lt;http://xmlns.com/foaf/0.1/&gt; .

&lt;http://example.org/people#joebob&gt; a foaf:Person;
  foaf:name &quot;Joe Bob&quot;;
  foaf:nick ( &quot;joe&quot; &quot;bob&quot; &quot;jaybee&quot; ) .</pre></div>

<div class="example"><div class="example-title"><span>Example 66</span>: Same example with a list of values in JSON-LD</div><pre class="example">{
  &quot;@context&quot;:
  {
    &quot;foaf&quot;: &quot;http://xmlns.com/foaf/0.1/&quot;
  },
  &quot;@id&quot;: &quot;http://example.org/people#joebob&quot;,
  &quot;@type&quot;: &quot;foaf:Person&quot;,
  &quot;foaf:name&quot;: &quot;Joe Bob&quot;,
  &quot;foaf:nick&quot;:
  {
    &quot;@list&quot;: [ &quot;joe&quot;, &quot;bob&quot;, &quot;jaybee&quot; ]
  }
}</pre></div>
</section>

</section>

<section id="rdfa">
<h3><span class="secno">D.2 </span>RDFa</h3>

<p>The following example describes three people with their respective names and
homepages.</p>

<div class="example"><div class="example-title"><span>Example 67</span>: RDFa fragment that describes three people</div><pre class="example">&lt;div <span class="diff">prefix=&quot;foaf: http://xmlns.com/foaf/0.1/&quot;</span>&gt;
   &lt;ul&gt;
      &lt;li <span class="diff">typeof=&quot;foaf:Person&quot;</span>&gt;
        &lt;a <span class="diff">rel=&quot;foaf:homepage&quot; href=&quot;http://example.com/bob/&quot; property=&quot;foaf:name&quot; </span>&gt;Bob&lt;/a&gt;
      &lt;/li&gt;
      &lt;li <span class="diff">typeof=&quot;foaf:Person&quot;</span>&gt;
        &lt;a <span class="diff">rel=&quot;foaf:homepage&quot; href=&quot;http://example.com/eve/&quot; property=&quot;foaf:name&quot; </span>&gt;Eve&lt;/a&gt;
      &lt;/li&gt;
      &lt;li <span class="diff">typeof=&quot;foaf:Person&quot;</span>&gt;
        &lt;a <span class="diff">rel=&quot;foaf:homepage&quot; href=&quot;http://example.com/manu/&quot; property=&quot;foaf:name&quot; </span>&gt;Manu&lt;/a&gt;
      &lt;/li&gt;
   &lt;/ul&gt;
&lt;/div&gt;</pre></div>

<p>An example JSON-LD implementation using a single <a class="tref internalDFN" title="context" href="#dfn-context">context</a> is
described below.</p>

<div class="example"><div class="example-title"><span>Example 68</span>: Same description in JSON-LD (context shared among node objects)</div><pre class="example">{
  &quot;@context&quot;:
  {
    &quot;foaf&quot;: &quot;http://xmlns.com/foaf/0.1/&quot;
  },
  &quot;@graph&quot;:
  [
    {
      &quot;@type&quot;: &quot;foaf:Person&quot;,
      &quot;foaf:homepage&quot;: &quot;http://example.com/bob/&quot;,
      &quot;foaf:name&quot;: &quot;Bob&quot;
    },
    {
      &quot;@type&quot;: &quot;foaf:Person&quot;,
      &quot;foaf:homepage&quot;: &quot;http://example.com/eve/&quot;,
      &quot;foaf:name&quot;: &quot;Eve&quot;
    },
    {
      &quot;@type&quot;: &quot;foaf:Person&quot;,
      &quot;foaf:homepage&quot;: &quot;http://example.com/manu/&quot;,
      &quot;foaf:name&quot;: &quot;Manu&quot;
    }
  ]
}</pre></div>

</section>

<section id="microformats">
<h3><span class="secno">D.3 </span>Microformats</h3>

<p>The following example uses a simple Microformats hCard example to express
how the Microformat is represented in JSON-LD.</p>

<div class="example"><div class="example-title"><span>Example 69</span>: HTML fragment with a simple Microformats hCard</div><pre class="example">&lt;div class=&quot;vcard&quot;&gt;
 &lt;a class=&quot;url fn&quot; href=&quot;http://tantek.com/&quot;&gt;Tantek Çelik&lt;/a&gt;
&lt;/div&gt;</pre></div>

<p>The representation of the hCard expresses the Microformat terms in the
<a class="tref internalDFN" title="context" href="#dfn-context">context</a> and uses them directly for the <code>url</code> and <code>fn</code>
properties. Also note that the Microformat to JSON-LD processor has
generated the proper URL type for <code>http://tantek.com/</code>.</p>

<div class="example"><div class="example-title"><span>Example 70</span>: Same hCard representation in JSON-LD</div><pre class="example">{
  &quot;@context&quot;:
  {
    &quot;vcard&quot;: &quot;http://microformats.org/profile/hcard#vcard&quot;,
    &quot;url&quot;:
    {
      &quot;@id&quot;: &quot;http://microformats.org/profile/hcard#url&quot;,
      &quot;@type&quot;: &quot;@id&quot;
    },
    &quot;fn&quot;: &quot;http://microformats.org/profile/hcard#fn&quot;
  },
  &quot;@type&quot;: &quot;vcard&quot;,
  &quot;url&quot;: &quot;http://tantek.com/&quot;,
  &quot;fn&quot;: &quot;Tantek Çelik&quot;
}</pre></div>

</section>

<section id="microdata">
<h3><span class="secno">D.4 </span>Microdata</h3>

<p>The microdata example below expresses book information as a microdata Work
item.
</p>

<div class="example"><div class="example-title"><span>Example 71</span>: HTML fragments that describes a book using microdata</div><pre class="example">&lt;dl itemscope
    itemtype=&quot;http://purl.org/vocab/frbr/core#Work&quot;
    itemid=&quot;http://purl.oreilly.com/works/45U8QJGZSQKDH8N&quot;&gt;
 &lt;dt&gt;Title&lt;/dt&gt;
 &lt;dd&gt;&lt;cite itemprop=&quot;http://purl.org/dc/terms/title&quot;&gt;Just a Geek&lt;/cite&gt;&lt;/dd&gt;
 &lt;dt&gt;By&lt;/dt&gt;
 &lt;dd&gt;&lt;span itemprop=&quot;http://purl.org/dc/terms/creator&quot;&gt;Wil Wheaton&lt;/span&gt;&lt;/dd&gt;
 &lt;dt&gt;Format&lt;/dt&gt;
 &lt;dd itemprop=&quot;http://purl.org/vocab/frbr/core#realization&quot;
     itemscope
     itemtype=&quot;http://purl.org/vocab/frbr/core#Expression&quot;
     itemid=&quot;http://purl.oreilly.com/products/9780596007683.BOOK&quot;&gt;
  &lt;link itemprop=&quot;http://purl.org/dc/terms/type&quot; href=&quot;http://purl.oreilly.com/product-types/BOOK&quot;&gt;
  Print
 &lt;/dd&gt;
 &lt;dd itemprop=&quot;http://purl.org/vocab/frbr/core#realization&quot;
     itemscope
     itemtype=&quot;http://purl.org/vocab/frbr/core#Expression&quot;
     itemid=&quot;http://purl.oreilly.com/products/9780596802189.EBOOK&quot;&gt;
  &lt;link itemprop=&quot;http://purl.org/dc/terms/type&quot; href=&quot;http://purl.oreilly.com/product-types/EBOOK&quot;&gt;
  Ebook
 &lt;/dd&gt;
&lt;/dl&gt;</pre></div>

<p>Note that the JSON-LD representation of the Microdata information stays
true to the desires of the Microdata community to avoid contexts and
instead refer to items by their full <a class="tref internalDFN" title="iri" href="#dfn-iri"><abbr title="Internationalized Resource Identifier">IRI</abbr></a>.</p>

<div class="example"><div class="example-title"><span>Example 72</span>: Same book description in JSON-LD (avoiding contexts)</div><pre class="example">[
  {
    &quot;@id&quot;: &quot;http://purl.oreilly.com/works/45U8QJGZSQKDH8N&quot;,
    &quot;@type&quot;: &quot;http://purl.org/vocab/frbr/core#Work&quot;,
    &quot;http://purl.org/dc/terms/title&quot;: &quot;Just a Geek&quot;,
    &quot;http://purl.org/dc/terms/creator&quot;: &quot;Whil Wheaton&quot;,
    &quot;http://purl.org/vocab/frbr/core#realization&quot;:
    [
      &quot;http://purl.oreilly.com/products/9780596007683.BOOK&quot;,
      &quot;http://purl.oreilly.com/products/9780596802189.EBOOK&quot;
    ]
  },
  {
    &quot;@id&quot;: &quot;http://purl.oreilly.com/products/9780596007683.BOOK&quot;,
    &quot;@type&quot;: &quot;http://purl.org/vocab/frbr/core#Expression&quot;,
    &quot;http://purl.org/dc/terms/type&quot;: &quot;http://purl.oreilly.com/product-types/BOOK&quot;
  },
  {
    &quot;@id&quot;: &quot;http://purl.oreilly.com/products/9780596802189.EBOOK&quot;,
    &quot;@type&quot;: &quot;http://purl.org/vocab/frbr/core#Expression&quot;,
    &quot;http://purl.org/dc/terms/type&quot;: &quot;http://purl.oreilly.com/product-types/EBOOK&quot;
  }
]</pre></div>
</section>
</section>

<section class="appendix informative" id="iana-considerations">

<!--OddPage-->
<h2><span class="secno">E. </span>IANA Considerations</h2><p><em>This section is non-normative.</em></p>

<p>This section is included merely for standards community review and will be
submitted to the Internet Engineering Steering Group if this specification
becomes a <abbr title="World Wide Web Consortium">W3C</abbr> Recommendation.</p>

<h2 id="application-ld-json">application/ld+json</h2>
<dl>
  <dt>Type name:</dt>
  <dd>application</dd>
  <dt>Subtype name:</dt>
  <dd>ld+json</dd>
  <dt>Required parameters:</dt>
  <dd>None</dd>
  <dt>Optional parameters:</dt>
  <dd>
    <dl>
      <dt><code>form</code></dt>
      <dd>Determines the serialization form for the JSON-LD document. The only
        valid value at the moment is <code>expanded</code>. If no form is
        specified in an HTTP request header to an HTTP server, the server <em class="rfc2119" title="may">may</em>
        choose any form. If no form is specified in an HTTP response, the form
        <em class="rfc2119" title="must not">must not</em> be assumed to take any particular form.</dd>
    </dl>
    <dl>
      <dt><code>profile</code></dt>
      <dd>A whitespace-separated list of IRIs identifying specific constraints
        or conventions that apply to a JSON-LD document. A profile <em class="rfc2119" title="must not">must not</em> change
        the semantics of the resource representation when processed without profile
        knowledge, so that clients both with and without knowledge of a profiled
        resource can safely use the same representation. The <code>profile</code>
        parameter <em class="rfc2119" title="may">may</em> also be used by clients to express their preferences in the
        content negotiation process. It is <em class="rfc2119" title="recommended">recommended</em> that profile IRIs are
        dereferenceable and provide useful documentation at that <abbr title="Internationalized Resource Identifier">IRI</abbr>. This
        specification, however, does not define any formats for such profile
        descriptions.
      </dd>
    </dl>
  </dd>
  <dt>Encoding considerations:</dt>
  <dd>The same as the <code>application/json</code> MIME media type.</dd>
  <dt>Security considerations:</dt>
  <dd>Since JSON-LD is intended to be a pure data exchange format for
    directed graphs, the serialization <em class="rfc2119" title="should not">should not</em> be passed through a
    code execution mechanism such as JavaScript's <code>eval()</code>
    function. It is <em class="rfc2119" title="recommended">recommended</em> that a conforming parser does not attempt to
    directly evaluate the JSON-LD serialization and instead purely parse the
    input into a language-native data structure. </dd>
  <dt>Interoperability considerations:</dt>
  <dd>Not Applicable</dd>
  <dt>Published specification:</dt>
  <dd>The <a href="http://json-ld.org/spec/latest/">JSON-LD</a> specification.</dd>
  <dt>Applications that use this media type:</dt>
  <dd>Any programming environment that requires the exchange of
    directed graphs. Implementations of JSON-LD have been created for
    JavaScript, Python, Ruby, PHP and C++.
  </dd>
  <dt>Additional information:</dt>
  <dd>
    <dl>
      <dt>Magic number(s):</dt>
      <dd>Not Applicable</dd>
      <dt>File extension(s):</dt>
      <dd>.jsonld</dd>
      <dt>Macintosh file type code(s):</dt>
      <dd>TEXT</dd>
    </dl>
  </dd>
  <dt>Person &amp; email address to contact for further information:</dt>
  <dd>Manu Sporny &lt;msporny@digitalbazaar.com&gt;</dd>
  <dt>Intended usage:</dt>
  <dd>Common</dd>
  <dt>Restrictions on usage:</dt>
  <dd>None</dd>
  <dt>Author(s):</dt>
  <dd>Manu Sporny, Gregg Kellogg, Markus Lanthaler, Dave Longley</dd>
  <dt>Change controller:</dt>
  <dd><abbr title="World Wide Web Consortium">W3C</abbr></dd>
</dl>

<p>Fragment identifiers used with <a href="#application-ld-json">application/ld+json</a>
  resources <em class="rfc2119" title="may">may</em> identify a node in a <a class="tref internalDFN" title="json-ld_graph" href="#dfn-json-ld_graph">JSON-LD graph</a> expressed in
  the resource. This idiom, which is also used in RDF [<cite><a class="bibref" href="#bib-RDF-CONCEPTS">RDF-CONCEPTS</a></cite>], gives a
  simple way to &quot;mint&quot; new, document-local IRIs to label nodes and therefore contributes
  considerably to the expressive power of JSON-LD.</p>

</section>

<section class="appendix informative" id="acknowledgements">

<!--OddPage-->
<h2><span class="secno">F. </span>Acknowledgements</h2><p><em>This section is non-normative.</em></p>

<p>A large amount of thanks goes out to the JSON-LD Community Group
participants who worked through many of the technical issues on the mailing
list and the weekly telecons - of special mention are Niklas Lindström,
François Daoust, Lin Clark, and Zdenko 'Denny' Vrandečić.
The editors would like to thank Mark Birbeck, who provided a great deal of
the initial push behind the JSON-LD work via his work on RDFj.
The work of Dave Lehn and Mike Johnson are appreciated for reviewing,
and performing several implementations of the specification. Ian Davis is
thanked for this work on RDF/JSON. Thanks also to Nathan Rixham,
Bradley P. Allen,
Kingsley Idehen, Glenn McDonald, Alexandre Passant, Danny Ayers, Ted
Thibodeau Jr., Olivier Grisel, Josh Mandel, Eric Prud'hommeaux,
David Wood, Guus Schreiber, Pat Hayes, Sandro Hawke, and Richard
Cyganiak for their input on the specification.
</p>
</section>



<section id="references" class="appendix" typeof="bibo:Chapter" resource="#references" rel="bibo:chapter">
<!--OddPage-->
<h2><span class="secno">G. </span>References</h2><section id="normative-references" typeof="bibo:Chapter" resource="#normative-references" rel="bibo:chapter"><h3><span class="secno">G.1 </span>Normative references</h3><dl class="bibliography" about=""><dt id="bib-BCP47">[BCP47]</dt><dd rel="dcterms:requires">A. Phillips; M. Davis. <a href="http://tools.ietf.org/html/bcp47"><cite>Tags for Identifying Languages</cite></a> September 2009. IETF Best Current Practice. URL: <a href="http://tools.ietf.org/html/bcp47">http://tools.ietf.org/html/bcp47</a> 
</dd><dt id="bib-RDF-CONCEPTS">[RDF-CONCEPTS]</dt><dd rel="dcterms:requires"><cite><a href="http://www.w3.org/TR/2011/WD-rdf11-concepts-20110830/">RDF 1.1 Concepts and Abstract Syntax</a></cite> Richard Cyganiak, David Wood, Editors. World Wide Web Consortium (work in progress). 30 May 2012. Editor's Draft. This edition of the JSON-LD Syntax specification is http://www.w3.org/TR/2011/WD-rdf11-concepts-20110830/. The <a href="http://www.w3.org/TR/rdf11-concepts/">latest edition of the JSON-LD Syntax</a> is available at http://www.w3.org/TR/rdf11-concepts/
</dd><dt id="bib-RFC2119">[RFC2119]</dt><dd rel="dcterms:requires">S. Bradner. <a href="http://www.ietf.org/rfc/rfc2119.txt"><cite>Key words for use in RFCs to Indicate Requirement Levels.</cite></a> March 1997. Internet RFC 2119.  URL: <a href="http://www.ietf.org/rfc/rfc2119.txt">http://www.ietf.org/rfc/rfc2119.txt</a> 
</dd><dt id="bib-RFC3987">[RFC3987]</dt><dd rel="dcterms:requires">M. Dürst; M. Suignard. <a href="http://www.ietf.org/rfc/rfc3987.txt"><cite>Internationalized Resource Identifiers (IRIs).</cite></a> January 2005. Internet RFC 3987. URL: <a href="http://www.ietf.org/rfc/rfc3987.txt">http://www.ietf.org/rfc/rfc3987.txt</a> 
</dd><dt id="bib-RFC4627">[RFC4627]</dt><dd rel="dcterms:requires">D. Crockford. <a href="http://www.ietf.org/rfc/rfc4627.txt"><cite>The application/json Media Type for JavaScript Object Notation (JSON)</cite></a> July 2006. Internet RFC 4627. URL: <a href="http://www.ietf.org/rfc/rfc4627.txt">http://www.ietf.org/rfc/rfc4627.txt</a>
</dd><dt id="bib-RFC5988">[RFC5988]</dt><dd rel="dcterms:requires"><cite><a href="http://tools.ietf.org/rfc/rfc5988">Web Linking</a></cite> M. Nottingham. Editor. October 2010. IETF Standard. URL: <a href="http://tools.ietf.org/rfc/rfc5988.txt">http://tools.ietf.org/rfc/rfc5988.txt</a>
</dd></dl></section><section id="informative-references" typeof="bibo:Chapter" resource="#informative-references" rel="bibo:chapter"><h3><span class="secno">G.2 </span>Informative references</h3><dl class="bibliography" about=""><dt id="bib-JSON-LD-API">[JSON-LD-API]</dt><dd rel="dcterms:references"><cite><a href="http://json-ld.org/spec/ED/json-ld-api/20120524/">The JSON-LD API 1.0</a></cite> Manu Sporny, Gregg Kellogg, Dave Longley, Markus Lanthaler, Editors. World Wide Web Consortium (work in progress). 24 May 2012. Editor's Draft. This edition of the JSON-LD Syntax specification is http://json-ld.org/spec/ED/json-ld-api/20120524/. The <a href="http://json-ld.org/spec/latest/json-ld-api/">latest edition of the JSON-LD Syntax</a> is available at http://json-ld.org/spec/latest/json-ld-api/
</dd><dt id="bib-RDF-SCHEMA">[RDF-SCHEMA]</dt><dd rel="dcterms:references">Dan Brickley; Ramanathan V. Guha. <a href="http://www.w3.org/TR/2004/REC-rdf-schema-20040210"><cite>RDF Vocabulary Description Language 1.0: RDF Schema.</cite></a> 10 February 2004. W3C Recommendation. URL: <a href="http://www.w3.org/TR/2004/REC-rdf-schema-20040210">http://www.w3.org/TR/2004/REC-rdf-schema-20040210</a> 
</dd><dt id="bib-RDFA-CORE">[RDFA-CORE]</dt><dd rel="dcterms:references">Shane McCarron; et al. <a href="http://www.w3.org/TR/2012/REC-rdfa-core-20120607/"><cite>RDFa Core 1.1: Syntax and processing rules for embedding RDF through attributes.</cite></a> 7 June 2012. W3C Recommendation. URL: <a href="http://www.w3.org/TR/2012/REC-rdfa-core-20120607/">http://www.w3.org/TR/2012/REC-rdfa-core-20120607/</a> 
</dd><dt id="bib-TURTLE-TR">[TURTLE-TR]</dt><dd rel="dcterms:references">Eric Prud'hommeaux, Gavin Carothers. <cite><a href="http://www.w3.org/TR/2011/WD-turtle-20110809/">Turtle: Terse RDF Triple Language.</a></cite> 09 August 2011. W3C Working Draft. URL: <a href="http://www.w3.org/TR/2011/WD-turtle-20110809/">http://www.w3.org/TR/2011/WD-turtle-20110809/</a>
</dd></dl></section></section></body></html>
